checkpatch: improve EXPORT_SYMBOL test for EXPORT_SYMBOL_NS uses

The EXPORT_SYMBOL test expects a single argument but definitions of
EXPORT_SYMBOL_NS have multiple arguments.

Update the test to extract only the first argument from any
EXPORT_SYMBOL related definition.

Link: https://lkml.kernel.org/r/9e8f251b42e405f460f26a23ba9b33ef45a94adc.camel@perches.com


Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Ian Pilcher <arequipeno@gmail.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>