tcg/arm: Use LDRD to load tlb mask+table

tcg/arm: Use LDRD to load tlb mask+table

This changes the code generation for the tlb from e.g.

	ldr      ip, [r6, #-0x10]
	ldr      r2, [r6, #-0xc]
	and      ip, ip, r4, lsr #8
	ldrd     r0, r1, [r2, ip]!
	ldr      r2, [r2, #0x18]

to

	ldrd     r0, r1, [r6, #-0x10]
	and      r0, r0, r4, lsr #8
	ldrd     r2, r3, [r1, r0]!
	ldr      r1, [r1, #0x18]

for armv7 hosts.  Rearranging the register allocation in
order to avoid overlap between the two ldrd pairs causes
the patch to be larger than it ordinarily would be.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>