src/*: Specify type of `CBFS_SIZE` once

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>