test: add sub-test and refactor fwk_module_check_call

Comments have been added to describe more the tests.
The tests have been moved down with respect to the function
declaration in fwk_module.h.

test_fwk_module_check_call_failed is now independent of the
order of execution of the tests.

Change-Id: Ia33a1a91eb742c883da5d6f81fc77258ce0a8f20
Signed-off-by: Elieva Pignat <Elieva.Pignat@arm.com>