* mips.h: Update documentation of "+s" and "+S".
opcodes/
* mips-opc.c (mips_builtin_opcodes): Use "+s" for "cins32" and
"+S" for "cins".
* mips-dis.c (print_mips_arg): Update "+s" and "+S" comments.
Combine cases.
gas/
* config/tc-mips.c (mips_ip): Preserve the real bit number for "+p".
Require the msb to be <= 31 for "+s". Check that the size is <= 31
for both "+s" and "+S".