kunit: Fix missing kerneldoc comment

Add a missing kerneldoc comment for the 'test' test context parameter,
fixing the following warning:

include/kunit/test.h:492: warning: Function parameter or struct member 'test' not described in 'kunit_kfree_const'
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/lkml/20240827160631.67e121ed@canb.auug.org.au/
Fixes: f2c6dbd2 ("kunit: Device wrappers should also manage driver name")
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

include/kunit/test.h

@@ -484,6 +484,7 @@ static inline void *kunit_kcalloc(struct kunit *test, size_t n, size_t size, gfp
 
 /**
  * kunit_kfree_const() - conditionally free test managed memory
+ * @test: The test context object.
  * @x: pointer to the memory
  *
  * Calls kunit_kfree() only if @x is not in .rodata section.