waitbit: Add the generic wait_for_bit macros for 16 and 32 bits.

wait_for_bit_le32 and wait_for_bit_le16 use the raw I/O functions
which would default to big-endian on BE systems. Create the generic
equivalents to use the native endianness.

Signed-off-by: Kursad Oney <kursad.oney@broadcom.com>
Reviewed-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>