HSI: remove deprecated IRQF_DISABLED

Remove the use of the IRQF_DISABLED flag
from drivers/hsi/clients/nokia-modem.c

It's a NOOP since 2.6.35 and it will be removed soon.

Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Sebastian Reichel <sre@kernel.org>