mb: remove duplicated Make code for spd.bin generation

Drop duplicated code for spd.bin generation that is provided globally
in lib/Makefile.inc.

For all affected boards it has been verified that the output binary
functionally matches the original one. The changed execution order of
Make instructions influenced the cbfs file order. Hence, the rom images
can't be compared directly.

Thus, the output files of the two timeless abuild runs have been compared.
Further, it was verified that the final files in cbfs stay identical, by
comparing the extracted cbfs of each board.

The boards (possibly) needing modification could be found with something
like this (with false positives, though):

find src/mainboard -name Makefile.inc | \
  xargs egrep 'SPD_BIN|SPD_DEPS' | cut -d: -f1 | sort -u

Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Change-Id: Icd3ac0fd6c901228554115c6350d88bb49874587
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44774
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/mainboard/google/hatch/Kconfig

@@ -81,6 +81,7 @@ config DIMM_SPD_SIZE
 config ROMSTAGE_SPD_CBFS
 	bool
 	default y if !ROMSTAGE_SPD_SMBUS
+	select GENERIC_SPD_BIN
 
 config ROMSTAGE_SPD_SMBUS
 	bool