[MCParser] Correctly handle CRLF line ends when consuming line comments

Fixes issue: https://bugs.llvm.org/show_bug.cgi?id=47983

The AsmLexer currently has an issue with lexing line comments in files
with CRLF line endings, in which it reads the carriage return as being
part of the line comment. This causes an error for certain valid comment
layouts; this patch fixes this by excluding the carriage return from the
line comment.

Differential Revision: https://reviews.llvm.org/D90234