[IRDA]: Fix IRQ save/restore handling in seq file handlers.

[IRDA]: Fix IRQ save/restore handling in seq file handlers.

IRDA was restoring IRQ flags in a different function from which they
were saved which explodes on certain platforms.  It did not need to
use _irq{save,restore}() anyways since the seqfile layer always invokes
these routines from user context with interrupts enabled, so using
plain spin_{lock,unlock}_irq() works just fine.