check_compliance: allow _MODULE variant of Kconfig options

Since b53a792f Zephyr has the ability to define tristate Kconfig
options. When a tristate option FOO is selected as a "module", this
results in autoconf.h defining CONFIG_FOO_MODULE, not CONFIG_FOO.

This patch allows the check_compliance script to also accept references
to a Kconfig symbol ending in _MODULE if the prefix is defined.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>