irda: Use __packed annotation instead IRDA_PACKED macro

Remove IRDA_PACKED macro, which maps to __attribute__((packed)). IRDA is
one of the last users of __attribute__((packet)). Networking code uses
__packed now.

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: David S. Miller <davem@davemloft.net>