fix return type error of rt_strcasecmp: rt_uint32_t to rt_int32_t

Signed-off-by: lihui <leehui_hrbeu71102@163.com>

include/rtthread.h

@@ -554,7 +554,7 @@ rt_int32_t rt_sscanf(const char *buf, const char *fmt, ...);
 char *rt_strncpy(char *dest, const char *src, rt_ubase_t n);
 void *rt_memmove(void *dest, const void *src, rt_ubase_t n);
 rt_int32_t rt_memcmp(const void *cs, const void *ct, rt_ubase_t count);
-rt_uint32_t rt_strcasecmp(const char *a, const char *b);
+rt_int32_t rt_strcasecmp(const char *a, const char *b);
 
 void rt_show_version(void);
 

src/kservice.c

@@ -370,7 +370,7 @@ RTM_EXPORT(rt_strstr);
  *
  * @return the result
  */
-rt_uint32_t rt_strcasecmp(const char *a, const char *b)
+rt_int32_t rt_strcasecmp(const char *a, const char *b)
 {
     int ca, cb;