image-uefi.conf: Add EFI_UKI_PATH variable

UEFI bootloader specification says the primary place for UKI images
is the /EFI/Linux/ directory under $boot. Defining a varaible for
the same to reuse in all UEFI-related packages.

(From OE-Core rev: f32a3f55a6602bb71effe28c931ac387f71af640)

Signed-off-by: Viswanath Kraleti <quic_vkraleti@quicinc.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/conf/image-uefi.conf

@@ -1,12 +1,16 @@
 # Location of EFI files inside EFI System Partition
 EFIDIR ?= "/EFI/BOOT"
 
+# Location of UKI inside EFI System Partition
+EFI_UKI_DIR ?= "/EFI/Linux"
+
 # Prefix where ESP is mounted inside rootfs. Set to empty if package is going
 # to be installed to ESP directly
 EFI_PREFIX ?= "/boot"
 
 # Location inside rootfs.
 EFI_FILES_PATH = "${EFI_PREFIX}${EFIDIR}"
+EFI_UKI_PATH = "${EFI_PREFIX}${EFI_UKI_DIR}"
 
 # The EFI name for the architecture
 EFI_ARCH ?= "INVALID"