[ELF] Delete dead SHT_NOBITS->SHT_PROGBITS code after r358981
[ELF] Delete dead SHT_NOBITS->SHT_PROGBITS code after r358981

After D60131/r358981, we no longer create SHT_NOBITS sections that may
contain ByteCommand (BYTE, SHORT, LONG, QUAD).

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@362108 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld