[committed] Fix HImode load mnemonic on microblaze port

[committed] Fix HImode load mnemonic on microblaze port

The tester recently started failing va-arg-22.c on microblaze-linux:

gcc.c-torture/execute/va-arg-22.c   -O0  (test for excess errors)

It was failing with an undefined reference to "r7" at link time.  This was
ultimately tracked down to a HImode load using (reg+reg) addressing mode, but
which used the lhui instruction instead of lhu.  The "i" means it's supposed to
be (reg+disp) so the assembler tried to interpret "r7" as an immediate/symbol.

The port uses %i<opnum> as an output modifier to select between sh/shi and
various other mnemonics for loads/stores.  The movhi pattern simply failed to
use it for the two cases where it's loading from memory (interestingly enough
it was used for stores).

Clearly we aren't using reg+reg much for HImode loads as this didn't fix
anything else in the testsuite.

gcc/
	* config/microblaze/microblaze.md (movhi): Use %i for half-word
	loads to properly select between lhu/lhui.