[Beignet] [PATCH] GBE: fix one potential register spilling bug.

[Song, Ruiling]

>         if ((regSize == ctx.getSimdWidth()/8 * GEN_REG_SIZE && family ==
> ir::FAMILY_DWORD)
> -          || (regSize == 2 * ctx.getSimdWidth()/8 * GEN_REG_SIZE &&
> family == ir::FAMILY_QWORD)) {
> +          || (regSize == 2 * ctx.getSimdWidth()/8 * GEN_REG_SIZE &&
> family == ir::FAMILY_QWORD)
> +          && !selection.isPartialWrite(reg)) {

Detect partial write through getOffsetReg() is OK for me.
But the above if (a||b &&c) condition check should be if ( (a || b) &&c). other parts LGTM.