staging: wilc1000: replace ISWILC1000() macro with inline function

Cleanup patch to avoid below checkpatch issue by replacing the macro
with inline function.

Macro argument 'id' may be better as '(id)' to avoid precedence issues.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>