[MTD] [NOR] Fix deadlock in Intel chip driver caused by get_chip recursion

This patch solves kernel deadlock issue seen on JFFF2 simultaneous 
operations. Detailed investigation of the issue showed that the kernel 
deadlock is caused by tons of recursive get_chip calls.

Signed-off-by: Alexey Korolev <akorolev@infradead.org>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>