riva_xaa: don't build RivaSetRopPattern when XAA is not supported
Fixes gcc warnings:
riva_xaa.c: In function ‘RivaSetRopPattern’:
riva_xaa.c:94:33: warning: implicit declaration of function ‘XAAGetPatternROP’; did you mean ‘RivaSetPattern’? [-Wimplicit-function-declaration]
pRiva->riva.Rop->Rop3 = XAAGetPatternROP(rop);
^~~~~~~~~~~~~~~~
RivaSetPattern
At top level:
riva_xaa.c:89:1: warning: ‘RivaSetRopPattern’ defined but not used [-Wunused-function]
RivaSetRopPattern(RivaPtr pRiva, int rop)
^~~~~~~~~~~~~~~~~