staging: panel: use schedule_timeout_interruptible()

API consolidation with coccinelle found:
./drivers/staging/panel/panel.c:782:2-18:
        consolidation with schedule_timeout_*() recommended

This is a 1:1 conversion with respect to schedule_timeout() to the
schedule_timeout_interruptible() helper only - so only an API
consolidation to improve readability. The timeout was being passed
as (ms * HZ + 999) / 1000 but that simply looks wrong - rather than
"manual" converting to jiffies, msecs_to_jiffies which handles all
corner-cases correctly, was used.

Patch was compile tested with x86_64_defconfig + CONFIG_STAGING=y,
CONFIG_PARPORT=m, CONFIG_PANEL=m

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>