X modesetting driver fails to start with cirrus KMS on QEMU/KVM since 3.19-rc.
The culprit is the commit 8975626ea35adcca561f8a81dedccfbc5dd8ec72
    drm/cirrus: allow 32bpp framebuffers for cirrus drm

Reverting this commit makes X working again.

X modesetting driver seems to try to open 1024x768x32 graphics, where the pitch
is 4096 and greater than max_pitch (4088) defined in
cirrus_check_framebuffer().
And it doesn't fall back to 24bpp as the patch expected.

Tested with 3.19-rc7 with qemu 2.1 -vga cirrus option.