part_efi: move uuid<->string conversion functions into lib/uuid.c

This commit introduces cleanup for uuid library.
Changes:
- move uuid<->string conversion functions into lib/uuid.c so they can be
  used by code outside part_efi.c.
- rename uuid_string() to uuid_bin_to_str() for consistency with existing
  uuid_str_to_bin()
- add an error return code to uuid_str_to_bin()
- update existing code to the new library functions.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: trini@ti.com

include/common.h

@@ -822,7 +822,8 @@ void	udelay        (unsigned long);
 void mdelay(unsigned long);
 
 /* lib/uuid.c */
-void uuid_str_to_bin(const char *uuid, unsigned char *out);
+void uuid_bin_to_str(unsigned char *uuid, char *str);
+int uuid_str_to_bin(char *uuid, unsigned char *out);
 int uuid_str_valid(const char *uuid);
 
 /* lib/vsprintf.c */