tcg/arm: bswap arguments in qemu_ld/st if needed On big endian targets, data arguments of qemu_ld/st ops have to be byte swapped. Two temporary registers are needed for qemu_st to do the bswap. r0 and r1 are used in system mode, do the same in user mode, which implies reworking the constraints. Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>