target/riscv/vector_helper.c: clean up reference of MTYPE

There's no code using MTYPE, which was a concept used in older vector
implementation.

Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Message-Id: <20230608053517.4102648-1-xiao.w.wang@intel.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/vector_helper.c

@@ -388,7 +388,7 @@ vext_ldst_us(void *vd, target_ulong base, CPURISCVState *env, uint32_t desc,
 
 /*
  * masked unit-stride load and store operation will be a special case of
- * stride, stride = NF * sizeof (MTYPE)
+ * stride, stride = NF * sizeof (ETYPE)
  */
 
 #define GEN_VEXT_LD_US(NAME, ETYPE, LOAD_FN)                            \
@@ -660,10 +660,6 @@ GEN_VEXT_LDFF(vle64ff_v, int64_t, lde_d)
 #define DO_MAX(N, M)  ((N) >= (M) ? (N) : (M))
 #define DO_MIN(N, M)  ((N) >= (M) ? (M) : (N))
 
-/* Unsigned min/max */
-#define DO_MAXU(N, M) DO_MAX((UMTYPE)N, (UMTYPE)M)
-#define DO_MINU(N, M) DO_MIN((UMTYPE)N, (UMTYPE)M)
-
 /*
  * load and store whole register instructions
  */