mips: move CONFIG_MIPS{32, 64} definition to config.mk

All mips32 boards define CONFIG_MIPS32 in config headers
except malta boards which define it in boards.cfg.
We can consolidate them by defining it in
arch/mips/cpu/mips32/config.mk.

CONFIG_MIPS64 definition can be moved to
arch/mips/cpu/mips64/config.mk as well.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Acked-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/boards.cfg b/boards.cfg
index 3664a2e..8ed627d 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -502,8 +502,8 @@
 Active  microblaze  microblaze     -           xilinx          microblaze-generic  microblaze-generic                   -                                                                                                                                 Michal Simek <monstr@monstr.eu>
 Active  mips        mips32         -           -               qemu-mips           qemu_mips                            qemu-mips:SYS_BIG_ENDIAN                                                                                                          Vlad Lungu <vlad.lungu@windriver.com>
 Active  mips        mips32         -           -               qemu-mips           qemu_mipsel                          qemu-mips:SYS_LITTLE_ENDIAN                                                                                                       -
-Active  mips        mips32         -           imgtec          malta               malta                                malta:MIPS32,SYS_BIG_ENDIAN                                                                                                       Paul Burton <paul.burton@imgtec.com>
-Active  mips        mips32         -           imgtec          malta               maltael                              malta:MIPS32,SYS_LITTLE_ENDIAN                                                                                                    Paul Burton <paul.burton@imgtec.com>
+Active  mips        mips32         -           imgtec          malta               malta                                malta:SYS_BIG_ENDIAN                                                                                                              Paul Burton <paul.burton@imgtec.com>
+Active  mips        mips32         -           imgtec          malta               maltael                              malta:SYS_LITTLE_ENDIAN                                                                                                           Paul Burton <paul.burton@imgtec.com>
 Active  mips        mips32         -           micronas        vct                 vct_platinum                         vct:VCT_PLATINUM                                                                                                                  -
 Active  mips        mips32         -           micronas        vct                 vct_platinum_onenand                 vct:VCT_PLATINUM,VCT_ONENAND                                                                                                      -
 Active  mips        mips32         -           micronas        vct                 vct_platinum_onenand_small           vct:VCT_PLATINUM,VCT_ONENAND,VCT_SMALL_IMAGE                                                                                      -