src/*: Specify type of CBFS_SIZE once

There's no need to specify the type of the `CBFS_SIZE` Kconfig symbol
more than once. This is done in `src/Kconfig`, along with its prompt.

Change-Id: I9e08e23e24e372e60c32ae8cd7387ddd4b618ddc
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56552
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-by:  Felix Singer <felixsinger@posteo.net>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/gm45/Kconfig

@@ -17,7 +17,6 @@ config VBOOT
 	select VBOOT_STARTS_IN_BOOTBLOCK
 
 config CBFS_SIZE
-	hex
 	default 0x100000
 
 config VGA_BIOS_ID

src/northbridge/intel/ironlake/Kconfig

@@ -18,7 +18,6 @@ config VBOOT
 	select TPM_STARTUP_IGNORE_POSTINIT
 
 config CBFS_SIZE
-	hex
 	default 0x100000
 
 config VGA_BIOS_ID

src/northbridge/intel/sandybridge/Kconfig

@@ -77,7 +77,6 @@ config NATIVE_RAMINIT_IGNORE_XMP_REQUESTED_VOLTAGE
 	  Handle with care!
 
 config CBFS_SIZE
-	hex
 	default 0x100000
 
 config VGA_BIOS_ID

src/northbridge/intel/x4x/Kconfig

@@ -15,7 +15,6 @@ config NORTHBRIDGE_SPECIFIC_OPTIONS
 	select HAVE_EXP_X86_64_SUPPORT
 
 config CBFS_SIZE
-	hex
 	default 0x100000 if !SOUTHBRIDGE_INTEL_I82801GX
 
 config VGA_BIOS_ID