Match: Allow more types truncation for .SAT_TRUNC

Match: Allow more types truncation for .SAT_TRUNC

The .SAT_TRUNC has the input and output types,  aka cvt from
itype to otype and the sizeof (otype) < sizeof (itype).  The
previous patch only allows the sizeof (otype) == sizeof (itype) / 2.
But actually we have 1/4 and 1/8 truncation.

This patch would like to support more types trunction when
sizeof (otype) < sizeof (itype).  The below truncation will be
covered.

* uint64_t => uint8_t
* uint64_t => uint16_t
* uint64_t => uint32_t
* uint32_t => uint8_t
* uint32_t => uint16_t
* uint16_t => uint8_t

The below test suites are passed for this patch:
1. The rv64gcv fully regression tests.
2. The rv64gcv build with glibc.
3. The x86 bootstrap tests.
4. The x86 fully regression tests.

gcc/ChangeLog:

	* match.pd: Allow any otype is less than itype truncation.

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