sh: make mm/asids-debugfs explicitly non-modular

The Makefile/Kconfig currently controlling compilation of this code is:

obj-$(CONFIG_DEBUG_FS)          += $(debugfs-y)
debugfs-y                       := asids-debugfs.o

lib/Kconfig.debug:config DEBUG_FS
lib/Kconfig.debug:      bool "Debug Filesystem"

....meaning that it currently is not being built as a module by anyone.

Lets remove the couple traces of modular code, so that when reading the
driver there is no doubt it is builtin-only.

Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: linux-sh@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Rich Felker <dalias@libc.org>