lib/uuid.c: introduce a few more generic helpers

lib/uuid.c: introduce a few more generic helpers

There are new helpers in this patch:

  uuid_is_valid		checks if a UUID is valid
  uuid_be_to_bin	converts from string to binary (big endian)
  uuid_le_to_bin	converts from string to binary (little endian)

They will be used in future, i.e. in the following patches in the series.

This also moves the indices arrays to lib/uuid.c to be shared accross
modules.

[[email protected]: fix typo]
Signed-off-by: Andy Shevchenko <[email protected]>
Reviewed-by: Matt Fleming <[email protected]>
Cc: Dmitry Kasatkin <[email protected]>
Cc: Mimi Zohar <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Jens Axboe <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>