cpu/x86/smm: Remove heap

Currently no smihandler uses heap.

coreboot's heap manager also is quite limited in what it will
free (only the latest alloc). This makes it a bad idea to use it inside
the smihandler, as depending on the alloc usage the heap might actually
be full at some point, breaking the smihandler.

This also reduces the ramstage by 448 bytes on google/vilboz.

Change-Id: I70cd822be17c1efe13c94a9dbd2e1038808b9c56
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64521
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/lib/Makefile.inc

@@ -215,7 +215,6 @@ romstage-y += boot_device.c
 ramstage-y += boot_device.c
 
 smm-y += boot_device.c
-smm-y += malloc.c
 smm-y += delay.c
 smm-y += fmap.c
 smm-y += cbfs.c memcmp.c