MIPS: BCM47xx: Make serial explicitly non-modular

The Makefile entry controlling compilation of this code is "obj-y"
meaning that it currently is not being built as a module by anyone.

Lets remove the couple traces of modular infrastructure use, 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.

We also delete the MODULE_LICENSE tag etc. since all that information
was (or is now) contained at the top of the file in the comments.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: "Rafał Miłecki" <zajec5@gmail.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13933/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>