lib: make test_bitops compilable into the kernel image

The test now is limited to be compiled as a module. There's no technical
reason for it. Now that the test bears some performance benchmarks, it
would be reasonable to run it at kernel load time, before userspace
starts, to reduce possible jitter.

Reviewed-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>

lib/Kconfig.debug

@@ -2436,7 +2436,6 @@ config TEST_LKM
 
 config TEST_BITOPS
 	tristate "Test module for compilation of bitops operations"
-	depends on m
 	help
 	  This builds the "test_bitops" module that is much like the
 	  TEST_LKM module except that it does a basic exercise of the