Fix LDM addressing mode disassembly

The Pixelflinger disassembler does not handle LDM addressing modes correctly,
assuming that the P and U bits in the instruction mean the same in both LDM and
STM. This results in the disassembler producing sequences like:

  stmfd r13!, {r4-r11, r14}
  ...
  ...
  ...
  ldmea r13!, {r4-r11, r14}

This small patch fixes it by EORing the P and U bits with the Load/Store bit.

Change-Id: Ic7a1556642c4e29415fc3697019f1239b6c26fc2