Convert CONFIG_SKIP_LOWLEVEL_INIT et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SKIP_LOWLEVEL_INIT
   CONFIG_SKIP_LOWLEVEL_INIT_ONLY

In order to do this, we need to introduce SPL and TPL variants of these
options so that we can clearly disable these options only in SPL in some
cases, and both instances in other cases.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/imgtec_xilfpga_defconfig b/configs/imgtec_xilfpga_defconfig
index 57077e4..ced7e03 100644
--- a/configs/imgtec_xilfpga_defconfig
+++ b/configs/imgtec_xilfpga_defconfig
@@ -1,8 +1,11 @@
 CONFIG_MIPS=y
+CONFIG_SKIP_LOWLEVEL_INIT=y
 CONFIG_SYS_MALLOC_F_LEN=0x600
 CONFIG_ENV_SIZE=0x4000
 CONFIG_DEFAULT_DEVICE_TREE="nexys4ddr"
 CONFIG_TARGET_XILFPGA=y
+CONFIG_MIPS_CACHE_SETUP=y
+CONFIG_MIPS_CACHE_DISABLE=y
 # CONFIG_MIPS_BOOT_ENV_LEGACY is not set
 CONFIG_MIPS_BOOT_FDT=y
 CONFIG_SYS_LOAD_ADDR=0x80500000