vfp: Get rid of a few warnings

src/core/arm/skyeye_common/vfp/vfpdouble.cpp

@@ -1064,7 +1064,7 @@ vfp_double_multiply(struct vfp_double *vdd, struct vfp_double *vdn,
 #define NEG_SUBTRACT	(1 << 1)
 
 static u32
-vfp_double_multiply_accumulate(ARMul_State* state, int dd, int dn, int dm, u32 fpscr, u32 negate, char *func)
+vfp_double_multiply_accumulate(ARMul_State* state, int dd, int dn, int dm, u32 fpscr, u32 negate, const char *func)
 {
     struct vfp_double vdd, vdp, vdn, vdm;
     u32 exceptions;

src/core/arm/skyeye_common/vfp/vfpsingle.cpp

@@ -957,7 +957,7 @@ vfp_single_multiply(struct vfp_single *vsd, struct vfp_single *vsn, struct vfp_s
 #define NEG_SUBTRACT	(1 << 1)
 
 static u32
-vfp_single_multiply_accumulate(ARMul_State* state, int sd, int sn, s32 m, u32 fpscr, u32 negate, char *func)
+vfp_single_multiply_accumulate(ARMul_State* state, int sd, int sn, s32 m, u32 fpscr, u32 negate, const char *func)
 {
     
     {