string: remove more pointless __HAVE_ARCH_STR*

None of these six macros are defined by any architecture. Moreover,
the ifndef guard only exists in either string.h or string.c, making them
completely pointless.

I'm not sure whether we have an explicit coding style discouraging the
"extern" qualifier on function declarations, and string.h has a random
mix of everything, but I can't leave it on strncasecmp() now that it
will be immediately after strcasecmp() which doesn't have it.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Rasmus Villemoes <rv@rasmusvillemoes.dk>

lib/string.c

@@ -399,7 +399,6 @@ void kfree_const(const void *x)
 }
 
 
-#ifndef __HAVE_ARCH_STRSPN
 /**
  * strspn - Calculate the length of the initial substring of @s which only
  *	contain letters in @accept
@@ -424,9 +423,7 @@ size_t strspn(const char *s, const char *accept)
 
 	return count;
 }
-#endif
 
-#ifndef __HAVE_ARCH_STRPBRK
 /**
  * strpbrk - Find the first occurrence of a set of characters
  * @cs: The string to be searched
@@ -444,9 +441,7 @@ char * strpbrk(const char * cs,const char * ct)
 	}
 	return NULL;
 }
-#endif
 
-#ifndef __HAVE_ARCH_STRTOK
 /**
  * strtok - Split a string into tokens
  * @s: The string to be searched
@@ -473,9 +468,7 @@ char * strtok(char * s,const char * ct)
 	___strtok = send;
 	return (sbegin);
 }
-#endif
 
-#ifndef __HAVE_ARCH_STRSEP
 /**
  * strsep - Split a string into tokens
  * @s: The string to be searched
@@ -501,7 +494,6 @@ char * strsep(char **s, const char *ct)
 
 	return sbegin;
 }
-#endif
 
 #ifndef __HAVE_ARCH_MEMSET
 /**