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/mt7620_rfb_defconfig b/configs/mt7620_rfb_defconfig
index 2b90727..5fd4b9d 100644
--- a/configs/mt7620_rfb_defconfig
+++ b/configs/mt7620_rfb_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
@@ -12,6 +13,8 @@
 CONFIG_DEBUG_UART_BASE=0xb0000c00
 CONFIG_DEBUG_UART_CLOCK=40000000
 CONFIG_ARCH_MTMIPS=y
+CONFIG_MIPS_CACHE_SETUP=y
+CONFIG_MIPS_CACHE_DISABLE=y
 CONFIG_RESTORE_EXCEPTION_VECTOR_BASE=y
 CONFIG_MIPS_BOOT_FDT=y
 CONFIG_DEBUG_UART=y