Match: Refactor the signed SAT_TRUNC match patterns [NFC]

Match: Refactor the signed SAT_TRUNC match patterns [NFC]

This patch would like to refactor the all signed SAT_TRUNC patterns,
aka:
* Extract type check outside.
* Re-arrange the related match pattern forms together.

The below test suites are passed for this patch.
* The rv64gcv fully regression test.
* The x86 bootstrap test.
* The x86 fully regression test.

gcc/ChangeLog:

	* match.pd: Refactor sorts of signed SAT_TRUNC match patterns

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