Revert "[MCAsmParser] .rept/.irp/.irpc: remove excess tail EOL in expansion"

This reverts commit c6e787f7.

parseEOL() would remove \n # after .endr, not recognizing the line marker.

```
// reduced from Linux kernel arch/x86/crypto/sha1_avx2_x86_64_asm.S
.rept 1
nop
.endr
# 512 "a.s"
```