SDL_syspower.c: remove redundant expression

src/power/linux/SDL_syspower.c

@@ -99,7 +99,7 @@ make_proc_acpi_key_val(char **_ptr, char **_key, char **_val)
 
     *(ptr++) = '\0';  /* terminate the key. */
 
-    while ((*ptr == ' ') && (*ptr != '\0')) {
+    while (*ptr == ' ') {
         ptr++;  /* skip whitespace. */
     }