Fix MIPS call-clobbered-*.c tests

[Jeff Law]

On 10/2/19 5:47 AM, Richard Sandiford wrote:
> Jeff pointed out that gcc.target/mips/call-clobbered-4.c started
> failing after the function-abi series.  This is because IRA used
> to treat partly call-clobbered registers as hard conflicts and
> so wouldn't consider them for -fcaller-saves.  Now that we treat
> call clobbers the same way regardless of where they come from,
> we can use $f21 as a caller-save register.  This in turn means
> that -Os is no longer a special case in call-clobbered-3.c.
> 
> (The new code is the same size as the old code.)
> 
> Tested on mipsel-linux-gnu.  OK to install?
> 
> Richard
> 
> 
> 2019-10-02  Richard Sandiford  <richard.sandiford@arm.com>
> 
> gcc/testsuite/
> 	* gcc.target/mips/call-clobbered-3.c: Remove skip for -Os.
> 	* gcc.target/mips/call-clobbered-4.c: Delete.
OK
jeff