drivers/char: make hpet.c explicitly non-modular

The Kconfig currently controlling compilation of this code is:

char/Kconfig:config HPET
char/Kconfig:   bool "HPET - High Precision Event Timer" if (X86 || IA64)

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

Lets remove the modular code that is essentially orphaned, 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 don't replace module.h with init.h since the file already has that.

Also note that MODULE_DEVICE_TABLE is a no-op for non-modular code.

We leave some tags like MODULE_AUTHOR for documentation purposes.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>