soc/intel/alderlake: Increase default CBFS size to 4MB

Updating some submodule pointers to their latest commit causes some
builds with default configuration to fail since all required components
don't fit into 2MB anymore. Specifically, this has been experienced with
the microcode and FSP submodules.

So, increase the default CBFS size to 4MB to make sure builds succeed
with updated submodules.

Change-Id: I2fc16240bef36c057608acadf3cb7c65e7f0d244
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76217
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/soc/intel/alderlake/Kconfig

@@ -378,7 +378,7 @@ config VBOOT_HASH_BLOCK_SIZE
 	default 0x1000
 
 config CBFS_SIZE
-	default 0x200000
+	default 0x400000
 
 config PRERAM_CBMEM_CONSOLE_SIZE
 	hex