[arm][committed] Clean up code iterator usage in satsi* patterns

[arm][committed] Clean up code iterator usage in satsi* patterns

GCC 10 now supports having RTL codes being code attributes (thanks
Richard) allowing us to map smax to smin and vice versa.
This means we can clean up their use in the saturation patterns that do
the cross product of [smin, smax] and use the pattern
predicate to cancel out the nonsense ones.

	* config/arm/arm.md (SATrev): Change to code attribute.
	(*satsi_<SAT:code>): Adjust for the above.
	(*satsi_<SAT:code>_shift): Likewise.

From-SVN: r273796