libfdt: replace ARCH_FIXUP_FDT with ARCH_FIXUP_FDT_MEMORY

Commit e2f88dfd2d96 ("libfdt: Introduce new ARCH_FIXUP_FDT option")
allows us to skip memory setup of DTB, but a problem for ARM is that
spin_table_update_dt() and psci_update_dt() are skipped as well if
CONFIG_ARCH_FIXUP_FDT is disabled.

This commit allows us to skip only fdt_fixup_memory_banks() instead
of the whole of arch_fixup_fdt().  It will be useful when we want to
use a memory node from a kernel DTB as is, but need some fixups for
Spin-Table/PSCI.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Alexey Brodkin <abrodkin@synopsys.com>
Acked-by: Simon Glass <sjg@chromium.org>
Fixed build error for x86:
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Kconfig b/Kconfig
index 529858a..58a9d9b 100644
--- a/Kconfig
+++ b/Kconfig
@@ -298,9 +298,8 @@
 	help
 	  TODO: Move CONFIG_SYS_CLK_FREQ for all the architecture
 
-config ARCH_FIXUP_FDT
-	bool "Enable arch_fixup_fdt() call"
-	depends on ARM || MIPS
+config ARCH_FIXUP_FDT_MEMORY
+	bool "Enable arch_fixup_memory_banks() call"
 	default y
 	help
 	  Enable FDT memory map syncup before OS boot. This feature can be