media: dvb-core: fix sleeping inside atomic context

Before calling the callback function to the upper layer
the demux spinlock is acquired with interrupts disabled,
For pull mode, the spinlock is later released to allow sleeping
until enough space is freed. However, releasing the spinlock
while interrupts are still disabled means we remain in an atomic
context so sleeping is not allowed.

Change-Id: Ief2c35837b2ff87222a26eef6dce4daa255d163d
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>