ACPIPHP: allow acpiphp to build without ACPI_DOCK

Change the build options for acpiphp so that it may build without being
dependent on the ACPI_DOCK option, but yet does not allow the option of
acpiphp being built-in when dock is built as a module.
This does not change the previous patch for ACPI_IBM_DOCK Kconfig.

For the following matrix of config options, I built an i386 kernel.

Dock		acpiphp		should it build?	confirmed
y		y		y			y
y		n		y			y
y		m		y			y
m		y		no - acpiphp should	acpiphp was 
				     convert to m	converted to m
m		n		y			y
m		m		y			y
n		y		y			y
n		n		y			y
n		m		y			y


Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>