Match: Support form 4 for unsigned integer .SAT_TRUNC

Match: Support form 4 for unsigned integer .SAT_TRUNC

This patch would like to support the form 4 of the unsigned integer
.SAT_TRUNC. Aka below example:

Form 4:
  #define DEF_SAT_U_TRUC_FMT_4(NT, WT)           \
  NT __attribute__((noinline))                   \
  sat_u_truc_##WT##_to_##NT##_fmt_4 (WT x)       \
  {                                              \
    bool not_overflow = x <= (WT)(NT)(-1);       \
    return ((NT)x) | (NT)((NT)not_overflow - 1); \
  }

DEF_SAT_U_TRUC_FMT_4(uint32_t, uint64_t)

Before this patch:
   4   │ __attribute__((noinline))
   5   │ uint8_t sat_u_truc_uint32_t_to_uint8_t_fmt_4 (uint32_t x)
   6   │ {
   7   │   _Bool not_overflow;
   8   │   unsigned char _1;
   9   │   unsigned char _2;
  10   │   unsigned char _3;
  11   │   uint8_t _6;
  12   │
  13   │ ;;   basic block 2, loop depth 0
  14   │ ;;    pred:       ENTRY
  15   │   not_overflow_5 = x_4(D) <= 255;
  16   │   _1 = (unsigned char) x_4(D);
  17   │   _2 = (unsigned char) not_overflow_5;
  18   │   _3 = _2 + 255;
  19   │   _6 = _1 | _3;
  20   │   return _6;
  21   │ ;;    succ:       EXIT
  22   │
  23   │ }

After this patch:
   4   │ __attribute__((noinline))
   5   │ uint8_t sat_u_truc_uint32_t_to_uint8_t_fmt_4 (uint32_t x)
   6   │ {
   7   │   uint8_t _6;
   8   │
   9   │ ;;   basic block 2, loop depth 0
  10   │ ;;    pred:       ENTRY
  11   │   _6 = .SAT_TRUNC (x_4(D)); [tail call]
  12   │   return _6;
  13   │ ;;    succ:       EXIT
  14   │
  15   │ }

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: Add form 4 for unsigned .SAT_TRUNC matching.

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