string: make memcpy src const

kernel-src/include/string.h

@@ -6,7 +6,7 @@
 size_t strlen(const char *str);
 char *strcpy(char *dest, const char *src);
 char *strcat(char *dest, const char *str);
-void *memcpy(void *dest, void *src, size_t size);
+void *memcpy(void *dest, const void *src, size_t size);
 void *memset(void *dest, unsigned long what, size_t size);
 int strcmp(const char *a, const char *b);
 int strncmp(const char *a, const char *b, size_t c);

kernel-src/lib/string.c

@@ -3,7 +3,7 @@
 #include <stdint.h>
 #include <errno.h>
 
-void *memcpy(void *d, void *s, size_t c) {
+void *memcpy(void *d, const void *s, size_t c) {
 #ifdef __x86_64__
 	asm volatile ("rep movsb" : : "S"(s), "D"(d), "c"(c) : "memory");
 #else