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/gardena-smart-gateway-mt7688_defconfig b/configs/gardena-smart-gateway-mt7688_defconfig
index 73260b5..b16a229 100644
--- a/configs/gardena-smart-gateway-mt7688_defconfig
+++ b/configs/gardena-smart-gateway-mt7688_defconfig
@@ -1,4 +1,5 @@
 CONFIG_MIPS=y
+CONFIG_SKIP_LOWLEVEL_INIT=y
 CONFIG_SPL_LIBCOMMON_SUPPORT=y
 CONFIG_SPL_LIBGENERIC_SUPPORT=y
 CONFIG_NR_DRAM_BANKS=1
@@ -15,6 +16,8 @@
 CONFIG_ENV_OFFSET_REDUND=0xB0000
 CONFIG_ARCH_MTMIPS=y
 CONFIG_SOC_MT7628=y
+CONFIG_MIPS_CACHE_SETUP=y
+CONFIG_MIPS_CACHE_DISABLE=y
 CONFIG_RESTORE_EXCEPTION_VECTOR_BASE=y
 # CONFIG_MIPS_BOOT_ENV_LEGACY is not set
 CONFIG_MIPS_BOOT_FDT=y