eliminate the "call" operand modifier from the asm descriptions, modeling

eliminate the "call" operand modifier from the asm descriptions, modeling
it as a pcrel immediate instead.  This gets pc-rel weirdness out of the
main printoperand codepath.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73829 91177308-0d34-0410-b5e6-96231b3b80d8