For bitmasks printing values in hex is more convenient.

Prefix with `0x` to make it clear, that it’s a hex value, and pad it
out.

Using the helper for `amdgpu.ppfeaturemask`, it will look like below.

Before:

    $ more /sys/module/amdgpu/parameters/ppfeaturemask
    4294950911

After:

    $ more /sys/module/amdgpu/parameters/ppfeaturemask
    0xffffbfff

Cc: linux-kernel@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/374726/