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

lib/Makefile

@@ -61,6 +61,7 @@ obj-y += string.o
 obj-y += time.o
 obj-$(CONFIG_TRACE) += trace.o
 obj-$(CONFIG_BOOTP_PXE) += uuid.o
+obj-$(CONFIG_PARTITION_UUIDS) += uuid.o
 obj-y += vsprintf.o
 obj-$(CONFIG_LIB_RAND) += rand.o