[AVR] Fix the 'call.ll' CodeGen test

Commit r343851 changed the format of the generated instructions.

An unnecessary load has been removed. Previously, a value would be moved
from r24 into a temporary register just to be copied into r30 before the
indirect call. Now, codegen immediately loads r24 into r30, saving a
MOVW instruction.

llvm-svn: 344111