Fix duplicate uuid_t typedef.

This typedef is being done in both lib/libefi/include/sys/uuid.h and
/usr/include/uuid/uuid.h, both of which are included in lib/libefi/rdwr_efi.c.

This leads to the following error:

In file included from ../../lib/libefi/include/sys/efi_partition.h:29,
                 from ../../lib/libefi/rdwr_efi.c:41:
../../lib/libefi/include/sys/uuid.h:81: error: redefinition of typedef 'uuid_t'
/usr/include/uuid/uuid.h:19: note: previous declaration of 'uuid_t' was here

The reason that we didn't see this before, is because of a strange feature in
gcc where some types of warnings/errors are silently ignored if they come from
system headers. But depending on the order of how system headers end up
included, libefi's uuid.h may actually be included after uuid/uuid.h, which
leads to the error above.

It is safe to remove this duplicate typedef because we are already
dependent on the linux uuid.h header and it's exceptionally unlikely
they will ever change the size.

lib/libefi/include/sys/uuid.h

@@ -74,12 +74,8 @@ struct uuid {
 	uint8_t		node_addr[6];
 };
 
-#define	UUID_LEN	16
-
 #define	UUID_PRINTABLE_STRING_LENGTH 37
 
-typedef uchar_t		uuid_t[UUID_LEN];
-
 /*
  * Convert a uuid to/from little-endian format
  */