kernel.bbclass: Fix incorrect deploying of fitimage.initramfs

kernel.bbclass: Fix incorrect deploying of fitimage.initramfs

When kernel-fitimage and initramfs is enabled using
INITRAMFS_IMAGE_BUNDLE = "1", kernel do_deploy tries to deploy
fitImage.initramfs with following error

| install: cannot stat 'arch/arm64/boot/fitImage.initramfs': No such
file or directory

Skip deploying fitimage.initramfs, since fitimage does not
create fitimage.initramfs

(From OE-Core rev: 0f87f8522a2c1b5a7042738887952b98060fbd9d)

Signed-off-by: Manjukumar Matha <manjukumar.harthikote-matha@xilinx.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>