Add dependency on pixman
Add dependency on pixman

The driver now directly calls pixman, so add it as a pkgconfig
dependency.

Change-Id: I0249709b023afaaa093c3a3f27c159c2f4b7b64b

xin3liang/xf86-video-armsoc,xin3liang/xf86-video-armsoc,Popolon/xf86-video-armsoc,freedesktop-unofficial-mirror/xorg__driver__xf86-video-armsoc,mmind/xf86-video-armsoc,Popolon/xf86-video-armsoc,singulared/xf86-video-armsoc,commshare/xf86-video-armsoc,singulared/xf86-video-armsoc,OtherCrashOverride/armsoc-hardkernel,mdrjr/xf86-video-armsoc,apxii/xf86-video-armsoc,mdrjr/xf86-video-armsoc,sbambrough/xf86-video-armsoc,OtherCrashOverride/armsoc-hardkernel,mmind/xf86-video-armsoc,sbambrough/xf86-video-armsoc,commshare/xf86-video-armsoc,freedesktop-unofficial-mirror/xorg__driver__xf86-video-armsoc,apxii/xf86-video-armsoc