isa: Decouple X86_32 dependency from the ISA Kconfig option

The introduction of the ISA_BUS option blocks the compilation of ISA
drivers on non-x86 platforms. The ISA_BUS configuration option should
not be necessary if the X86_32 dependency can be decoupled from the ISA
configuration option. This patch both removes the ISA_BUS configuration
option entirely and removes the X86_32 dependency from the ISA
configuration option.

Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>