image-fitimage: add FIT_LINUX_BIN variable

Add FIT_LINUX_BIN variable to image-fitimage.conf to allow control over
kernel section inclusion.

Suggested-by: Adrian Freihofer <adrian.freihofer@siemens.com>
(From OE-Core rev: d077777cbdb4b00eb424289e85fe661f69a9877a)

Signed-off-by: Kavinaya S <kavinaya@qti.qualcomm.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/conf/image-fitimage.conf

@@ -37,6 +37,13 @@ FIT_CONF_PREFIX[doc] = "Prefix to use for FIT configuration node name"
 
 FIT_SUPPORTED_INITRAMFS_FSTYPES ?= "cpio.lz4 cpio.lzo cpio.lzma cpio.xz cpio.zst cpio.gz ext2.gz cpio"
 
+# Allow user to support special use cases where the kernel binary is
+# not included in the FIT image itself.
+# This is particularly useful for UKI-based setups, where the kernel
+# and initramfs are bundled into a Unified Kernel Image (UKI), and
+# DTBs are provided separately in a FIT image.
+FIT_LINUX_BIN ?= "linux.bin"
+
 # Allow user to select the default DTB for FIT image when multiple dtb's exists.
 FIT_CONF_DEFAULT_DTB ?= ""