arm/edk2-firmware: mark as machine-specific

As this recipe needs per-machine configuration to be set, mark the
package archicture as the machine architecture to ensure that multiple
BSPs don't conflict in the package feed.

Change-Id: I3db0be2621987290a0c9e7b689554cd5f51cb61e
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/recipes-bsp/uefi/edk2-firmware_git.bb

@@ -35,6 +35,7 @@ inherit deploy
 B = "${WORKDIR}/build"
 S = "${WORKDIR}/git"
 
+PACKAGE_ARCH = "${MACHINE_ARCH}"
 COMPATIBLE_MACHINE ?= "invalid"
 
 LDFLAGS[unexport] = "1"