cb/kabylake: don't hardcode power_on_after_fail

I realised that the Dell OptiPlex 3050 Micro has NVRAM available.
Use that backend, and hardcode power_on_after_fail to Disable,
which is already done in cmos.default.

The Lenovo ThinkPad T480 currently has no option table in coreboot,
besides the CBFS one. For this, the CBFS option table has been
enabled, and the build system has been modified to insert
a relevant config for power_on_after_fail.

Nicholas Chin informs me that Kabylake generally has legacy NVRAM,
so enabling it for the T480/T480s should work, but we'll need
to use it in the future anyway; better to just use CBFS now.

I *could* use the CBFS backend on 3050micro as well.

Signed-off-by: Leah Rowe <leah@libreboot.org>

config/coreboot/t480_vfsp_16mb/cbfs.cfg

@@ -0,0 +1 @@
+power_on_after_fail 0

config/coreboot/t480_vfsp_16mb/config/libgfxinit_corebootfb

@@ -16,8 +16,8 @@ CONFIG_COMPILER_GCC=y
 # CONFIG_IWYU is not set
 # CONFIG_FMD_GENPARSER is not set
 # CONFIG_UTIL_GENPARSER is not set
-CONFIG_OPTION_BACKEND_NONE=y
-# CONFIG_USE_CBFS_FILE_OPTION_BACKEND is not set
+# CONFIG_OPTION_BACKEND_NONE is not set
+CONFIG_USE_CBFS_FILE_OPTION_BACKEND=y
 CONFIG_COMPRESS_RAMSTAGE_LZMA=y
 # CONFIG_COMPRESS_RAMSTAGE_LZ4 is not set
 CONFIG_SEPARATE_ROMSTAGE=y

config/coreboot/t480_vfsp_16mb/config/libgfxinit_txtmode

@@ -16,8 +16,8 @@ CONFIG_COMPILER_GCC=y
 # CONFIG_IWYU is not set
 # CONFIG_FMD_GENPARSER is not set
 # CONFIG_UTIL_GENPARSER is not set
-CONFIG_OPTION_BACKEND_NONE=y
-# CONFIG_USE_CBFS_FILE_OPTION_BACKEND is not set
+# CONFIG_OPTION_BACKEND_NONE is not set
+CONFIG_USE_CBFS_FILE_OPTION_BACKEND=y
 CONFIG_COMPRESS_RAMSTAGE_LZMA=y
 # CONFIG_COMPRESS_RAMSTAGE_LZ4 is not set
 CONFIG_SEPARATE_ROMSTAGE=y