string: move strdup() & strconcat() to lib/string.c

Move functions not available in PRE_RAM into seperate file.
Makes it easier to share code between rom and ramstage.

Change-Id: I0b9833fbf6742d110ee4bfc00cd650f219aebb2c
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
Reviewed-on: https://review.coreboot.org/c/31141
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/include/string.h

@@ -23,6 +23,8 @@ void *memchr(const void *s, int c, size_t n);
 int snprintf(char *buf, size_t size, const char *fmt, ...);
 int vsnprintf(char *buf, size_t size, const char *fmt, va_list args);
 #endif
+char *strdup(const char *s);
+char *strconcat(const char *s1, const char *s2);
 
 // simple string functions
 
@@ -51,26 +53,6 @@ static inline char *strchr(const char *s, int c)
 	return 0;
 }
 
-#if !defined(__PRE_RAM__)
-static inline char *strdup(const char *s)
-{
-	size_t sz = strlen(s) + 1;
-	char *d = malloc(sz);
-	memcpy(d, s, sz);
-	return d;
-}
-
-static inline char *strconcat(const char *s1, const char *s2)
-{
-	size_t sz_1 = strlen(s1);
-	size_t sz_2 = strlen(s2);
-	char *d = malloc(sz_1 + sz_2 + 1);
-	memcpy(d, s1, sz_1);
-	memcpy(d + sz_1, s2, sz_2 + 1);
-	return d;
-}
-#endif
-
 /**
  * Find a character in a string.
  *