code-guideline: Tag name should be a unique identifier

Following are the changes to variable names that are matching
with tag names (Rule 5.7 violations)

In kernel.h, event_type is matching with a tag name in
lib/os/onoff.c. Added a _ prefix to event_type and
also to the macro argument names.

In userspace.c, *dyn_obj is matching with the tag name
dyn_obj in the file itslef. Changed it to dyn

In device.h, device_mmio.h, init.h and init.c,
changed the *device to dev. Except for one change in
init.h

Signed-off-by: Spoorthy Priya Yerabolu <spoorthy.priya.yerabolu@intel.com>