mn10300 gas: `mov pc,aN' adds `pc' to symbol table

[Alexandre Oliva]

Assembling `mov pc,a[0-3]' after `.am33' would get `pc' added to the
symbol table, even though the insn is correctly assembled as copying
the program counter to one of the address registers.  That was because
other variants of the `mov' insn are tried first, and `pc' wasn't
recognized as a register name, so we ended up reading it as an
expression, which causes symbol_find_or_make() to be called on the
given name.  This patch fixes this problem.  Ok to install?