drivers: net: irda: bfin_sir: fix compile error

Bit IREN is replaced by UMOD_IRDA and UMOD_MASK since blackfin 60x added, but
this driver didn't update which will cause bfin_sir build error:

drivers/net/irda/bfin_sir.c:161:9: error: 'IREN' undeclared (first use in this
function)
drivers/net/irda/bfin_sir.c:435:18: error: 'IREN' undeclared (first use in
this function)
drivers/net/irda/bfin_sir.c:521:11: error: 'IREN' undeclared (first use in
this function)

This patch fix it.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
Acked-by: Samuel Ortiz <samuel@sortiz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>