fix v7 build register error, test=develop

lite/backends/arm/math/gemm_prepacked_int8.cc

@@ -2026,7 +2026,8 @@ inline void gemm_sdot_int8_kernel(const int8_t* a_ptr,
   "vadd.f32 q3, q11, q3\n"   /* r21, add offset */     \
   "vadd.f32 q4, q12, q4\n"   /* r30, add offset */     \
   "vadd.f32 q5, q13, q5\n"   /* r31, add offset */     \
-  "vld1.32 {d12-d13}, [%[vmax]]\n" /* set q4 = -127 \n"*/   \
+  /*"vld1.32 {d12-d13}, [%[vmax]]\n"*/ /* set q4 = -127 \n"*/   \
+  "vmov.f32 q6, #-127.0\n" \
   "vcge.f32 q7, q8, q6\n"   /* @ q8 >= -127 \n */     \
    "vcge.f32 q10, q9, q6\n"   /* @ q8 >= -127 \n */     \
   "vcge.f32 q11, q0, q6\n"   /* @ q8 >= -127 \n */     \
@@ -2130,7 +2131,7 @@ inline void gemm_int8_kernel(const int8_t* a_ptr,
                              int is_relu,
                              int k,
                              int rem) {
-  float vmax[4] = {-127.0, -127.0, -127.0, -127.0};
+  //float vmax[4] = {-127.0, -127.0, -127.0, -127.0};
   asm volatile(GEMM_INT8_KERNEL GEMM_INT8_INT8_OUT
                : [a_ptr] "+r"(a_ptr),
                  [b_ptr] "+r"(b_ptr),
@@ -2143,7 +2144,7 @@ inline void gemm_int8_kernel(const int8_t* a_ptr,
                  [alpha] "r"(alpha),
                  [bias] "r"(bias),
                  [rem] "r"(rem),
-                 [vmax] "r"(vmax),
+    //             [vmax] "r"(vmax),
                  [scale] "r"(scale)
                : "q0",
                  "q1",