[committed] MIPS/GAS: Correct `-O0' and `-O' option help, add `-O1' and `-O2'

[Maciej W. Rozycki]

Match commit 4ffff32f75b1 ("Match mips_optimize to the -O option 
supplied") and adjust `--help' output for `-O0', `-O', `-O1' and `-O2' 
options.

	gas/
	* config/tc-mips.c (md_show_usage): Correct help text for `-O0' 
	and `-O'.  Mention `-O1'.  Add `-O2' and its description.
---
 gas/config/tc-mips.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

binutils-mips-gas-o-help.diff
Index: binutils/gas/config/tc-mips.c
===================================================================
--- binutils.orig/gas/config/tc-mips.c	2018-05-14 02:15:03.000000000 +0100
+++ binutils/gas/config/tc-mips.c	2018-06-10 01:19:13.102144856 +0100
@@ -20002,8 +20002,9 @@ MIPS options:\n\
 -mgp32			use 32-bit GPRs, regardless of the chosen ISA\n\
 -mfp32			use 32-bit FPRs, regardless of the chosen ISA\n\
 -msym32			assume all symbols have 32-bit values\n\
--O0			remove unneeded NOPs, do not swap branches\n\
--O			remove unneeded NOPs and swap branches\n\
+-O0			do not remove unneeded NOPs, do not swap branches\n\
+-O, -O1			remove unneeded NOPs, do not swap branches\n\
+-O2			remove unneeded NOPs and swap branches\n\
 --trap, --no-break	trap exception on div by 0 and mult overflow\n\
 --break, --no-trap	break exception on div by 0 and mult overflow\n"));
   fprintf (stream, _("\