scripts/kernel-doc: fix parsing of function pointers

kernel-doc fails to parse function definitions like the one below

efi_status_t efi_create_event(uint32_t type, efi_uintn_t notify_tpl,
			      void (EFIAPI *notify_function) (
					struct efi_event *event,
					void *context),
			      void *notify_context, efi_guid_t *group,
			      struct efi_event **event)
{

due to the "EFIAPI" attribute preceding the function name.

cf. https://lkml.org/lkml/2018/9/3/1185



Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>