Match: Add widen_mul based unsigned SAT_MUL after gimple_convert refactor

Match: Add widen_mul based unsigned SAT_MUL after gimple_convert refactor

The build_and_insert_cast refactored to go the gimple_convert way, to
take care of the widen_mul.  Thus, the gimple layout from uint64_t
widen_mul to uint128_t doesn't need additional cast like other types
(uint32_t, uint16_t, uint8_t) widen to uint128_t for mul.  Thus, add
the simplifed pattern match for such forms of unsigned SAT_MUL.

The below test suites are passed for this patch:
1. The rv64gcv fully regression tests.
2. Fix rv64gcv SAT_MUL test failure of optimized .SAT_MUL check.
3. The x86 bootstrap tests.
4. The x86 fully regression tests.

gcc/ChangeLog:

	* match.pd: Add simplifed pattern for widen_mul based unsigned
	SAT_MUL.

Signed-off-by: Pan Li <pan2.li@intel.com>