qemu script: explicitly set 32 bit depth

qemu script: explicitly set 32 bit depth

Qemu update from 1.2 to 1.4 now allows for 16bit depth in guests,
whereby previously only 32bit depth was supported. However,
the new support is broken, so we force 32bit depth in all cases.

MUST_REVERT: on qemu update, if 16bit depth support is working ok

Fixes [YOCTO #3828]

(From OE-Core rev: 354377789628d96fa589cb5721134f631815cfeb)

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>