of: Fix export of of_find_matching_node_and_match()

Commit 50c8af4cf9, "of: introduce for_each_matching_node_and_match()"
renamed of_find_matching_node() to of_find_matching_node_and_match() and
created a new static inline of_find_matching_node() wrapper around the
new name. However, the change neglected to change the EXPORT_SYMBOL()
reference causing build errors for modules.

This patch fixes the EXPORT_SYMBOL() statement. Discovered on a PowerPC
Efika build with the mpc52xx_uart driver being built as a module.

Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>