ar71xx: fix initramfs image generation for Cameo933x profiles

Initramfs images are not generated for profiles which
are using the squashfs-only template. Add the missing
'Image/Build/Template/squashfs-only/initramfs' to fix
that.

Also, 'Image/Build/Cameo933x/initramfs' uses wrong
parameters for 'MkuImageLzma/initramfs' due to a
misplaced commma. Remove that to fix the generated
initramfs images.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@37871 3c298f89-4303-0410-b956-a3cf2f4a3e73