checkpatch: check symlinks while searching compatible strings

"grep -r" option excludes symlinks. This breaks if there are symlinks
present in the bindings and actual source resides outside of the kernel.
To consider symlinks invoke grep with "-R" option.

Change-Id: Ie43876a0caee8f7f5a217391213cbb12efd52ff9
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>