scatterlist: do not disable IRQs in sg_copy_buffer

scatterlist: do not disable IRQs in sg_copy_buffer

Commit 50bed2e2862a ("sg: disable interrupts inside sg_copy_buffer")
introduced disabling interrupts in sg_copy_buffer() since atomic uses of
miter required it due to use of kmap_atomic().

However, as commit 8290e2d2dcbf ("scatterlist: atomic sg_mapping_iter()
no longer needs disabled IRQs") acknowledges disabling interrupts is no
longer needed for calls to kmap_atomic() and therefore unneeded for
miter ops either, so remove it from sg_copy_buffer().

Link: http://lkml.kernel.org/r/1486040150-14109-3-git-send-email-gilad@benyossef.com
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <ofir.drang@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>