microblaze: Fixed bug in lshrsi3_with_size_opt

There is  a bug with the existing lshrsi3_with_size_opt pattern.
The first srl is the pattern is correct, and is presumably used to handle signed/unsigned shift, but the addk is wrong.
Adding does a left-shift instead of right-shift. The correct code would have been srl %0,%0.

Signed-off-by:Nagaraju <nmekala@xilix.com>
microblaze: Added load and store reverse patterns

Added the lwr/swr instructions pattern.
lwr and swr instructions will load/store the data with opposite endianness.

Signed-off-by:Nagaraju <nmekala@xilix.com>