soc/amd: remove root of SoC directory from include path

We shouldn't be providing -I include paths to the root of the soc
specific directory. It allows for lazy includes that can collide,
but there's no way of knowing the winning path since the winning
path is determined by Makefile.inc parsing order.

This is taken from CB:41355

Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I45ed219e4e0cccf3d4f04cc70dc1ef77c518afff
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60201
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/soc/amd/picasso/Makefile.inc

@@ -54,7 +54,6 @@ endif
 smm-y += gpio.c
 smm-y += smu.c
 
-CPPFLAGS_common += -I$(src)/soc/amd/picasso
 CPPFLAGS_common += -I$(src)/soc/amd/picasso/include
 CPPFLAGS_common += -I$(src)/soc/amd/picasso/acpi
 CPPFLAGS_common += -I$(src)/vendorcode/amd/fsp/picasso

src/soc/amd/stoneyridge/Makefile.inc

@@ -66,7 +66,6 @@ smm-$(CONFIG_DEBUG_SMI) += uart.c
 smm-y += gpio.c
 smm-y += psp.c
 
-CPPFLAGS_common += -I$(src)/soc/amd/stoneyridge
 CPPFLAGS_common += -I$(src)/soc/amd/stoneyridge/include
 CPPFLAGS_common += -I$(src)/soc/amd/stoneyridge/acpi