Makefile.inc: Generate master header and pointer as C structs

The makefiles don't like cbfs file names with spaces in them so update
the file name with '_' instead of spaces. To keep the master header at
the top of cbfs, add a placeholder.

This removes the need to handle the cbfs master header in cbfstool.
This functionality will be dropped in a later CL.

On x86 reserve some space in the linker script to add the pointer.
On non-x86 generate a pointer inside a C struct file.

As a bonus this would actually fix the master header pointer mechanism
on Intel/APL as only the bootblock inside IFWI gets memory mapped.

TESTED on thinkpad X201: SeaBIOS correctly finds the cbfs master
header.

Change-Id: I3ba01be7da1f09a8cac287751497c18cda97d293
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59132
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/security/vboot/Makefile.inc

@@ -175,6 +175,8 @@ regions-for-file = $(subst $(spc),$(comma),$(sort \
 		$(regions-for-file-$(1)), \
 		$(if $(filter $(if $(filter y,$(CONFIG_VBOOT_STARTS_IN_ROMSTAGE)), \
 			%/romstage,) \
+		header_pointer \
+		cbfs_master_header \
 		mts \
 		%/verstage \
 		locales \