kernel: add kmod-fb-sys-ram

The kernel modules that provide support for framebuffers in system RAM
are currently included in the kmod-drm-imx package. Move them to a
separate package, so that other modules can depend on them.

Increase the autoload order of the drm-imx* packages to load the modules
after loading the fb modules they depend on.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>