MC: Remove errant EatToEndOfStatement() in asm parser.

The caller is already responsible for eating any additional input on the
line. Putting an additional EatToEndOfStatement() in ParseStatement()
causes an entire extra statement to be consumed when treating warnings
as errors. For example, test/MC/macros.s will assert() because the
.endmacro directive is missed as a result.

rdar://11355843

llvm-svn: 155925