ACPI: ibm-acpi: organize code

Shuffle code around to better organize the driver code inside the
ibm-acpi.c file.

This patch adds no functional changes.  It is pure fluff that will make me
a bit more productive.
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>