pixman: Apply upstream patch to fix compilation on MIPS

Fixes:
http://autobuild.buildroot.net/results/38aa4f2a2269b80226b910c46e0c9abe7dc38ff8/

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>