soc/amd/mendocino/psp_verstage/Makefile.inc: Remove path to non-existent directory

Found using 'Wmissing-include-dirs' command option.
Fix:
cc1: error: ../../src/soc/amd/mendocino/psp_verstage/include: No such file or directory [-Werror=missing-include-dirs]

Change-Id: I1cc084abc7a9bfed760350f304dd074081a7eebf
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/71586
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>
diff --git a/src/soc/amd/mendocino/psp_verstage/Makefile.inc b/src/soc/amd/mendocino/psp_verstage/Makefile.inc
index b185ffd..19dd8a7 100644
--- a/src/soc/amd/mendocino/psp_verstage/Makefile.inc
+++ b/src/soc/amd/mendocino/psp_verstage/Makefile.inc
@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
-verstage-generic-ccopts += -I$(src)/soc/amd/mendocino/psp_verstage/include
 verstage-generic-ccopts += -I$(src)/vendorcode/amd/fsp/mendocino/include
 
 verstage-generic-ccopts += -I$(src)/soc/amd/common/psp_verstage/include