[llvm-readobj][mips] Remove non-standard --misp-xxx flags
[llvm-readobj][mips] Remove non-standard --misp-xxx flags

llvm-readobj "non-standard" flags `--mips-plt-got`, `--mips-abi-flags`,
`--mips-reginfo`, and `--mips-options` are superseded by the `--arch-specific`
flag and can be removed now.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@373590 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm