mtd: rawnand: export NAND operation tracer

The NAND core has a NAND operation tracing function, but it can only
be used by drivers using the generic option parser from the NAND core.
Export the tracing function as a static inline function in rawnand.h
so that drivers implementing exec_op directly do not have to write their
own operation tracing.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>