powerpc/e6500: hw tablewalk: optimize a bit for tcd lock acquiring codes

It makes no sense to put the instructions for calculating the lock
value (cpu number + 1) and the clearing of eq bit of cr1 in lbarx/stbcx
loop. And when the lock is acquired by the other thread, the current
lock value has no chance to equal with the lock value used by current
cpu. So we can skip the comparing for these two lock values in the
lbz/bne loop.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>