cbfs: Enable CBFS mcache on most chipsets

This patch flips the default of CONFIG_NO_CBFS_MCACHE so the feature is
enabled by default. Some older chipsets with insufficient SRAM/CAR space
still have it explicitly disabled. All others get the new section added
to their memlayout... 8K seems like a sane default to start with.

Change-Id: I0abd1c813aece6e78fb883f292ce6c9319545c44
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38424
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/arch/x86/Kconfig

@@ -144,6 +144,13 @@ config PRERAM_CBMEM_CONSOLE_SIZE
 	help
 	  Increase this value if preram cbmem console is getting truncated
 
+config CBFS_MCACHE_SIZE
+	hex
+	depends on !NO_CBFS_MCACHE
+	default 0x2000
+	help
+	  Increase this value if you see CBFS mcache overflow warnings.
+
 config PC80_SYSTEM
 	bool
 	default y if ARCH_X86

src/arch/x86/car.ld

@@ -48,6 +48,9 @@
 
 	TIMESTAMP(., 0x200)
 
+#if !CONFIG(NO_CBFS_MCACHE)
+	CBFS_MCACHE(., CONFIG_CBFS_MCACHE_SIZE)
+#endif
 #if !CONFIG(NO_FMAP_CACHE)
 	FMAP_CACHE(., FMAP_SIZE)
 #endif