Check for closest render-to-tex, ignore high bits of fb addr

Tested on a real PSP:

sceGuDepthBuffer((void *)((intptr_t)dbp0 | 0x99000000), 512);
sceGuDrawBuffer(GU_PSM_8888, (void *)((intptr_t)fbp0 | 0x99000000), 512);

Still draws exactly the same place.  Tried a couple other combinations to be sure.  I think we should just ignore the high bits entirely.

@solarmystic does this (specifically the closest framebuffer) help Breath of Fire 3?

-[Unknown]