isa: Remove ISA_BUS_API selection for ISA_BUS

ISA_BUS_API is selected by drivers themselves when necessary. The
ISA_BUS Kconfig option is now simply a mask for true ISA device drivers
and relevant configuration. For now, the ISA_BUS Kconfig option is only
available for X86, but may be added for other arch builds in the future
if the need arises.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/x86/Kconfig

@@ -2635,11 +2635,13 @@ config PCI_CNB20LE_QUIRK
 source "drivers/pci/Kconfig"
 
 config ISA_BUS
-	bool "ISA-style bus support on modern systems" if EXPERT
-	select ISA_BUS_API
+	bool "ISA bus support on modern systems" if EXPERT
 	help
-	  Enables ISA-style drivers on modern systems. This is necessary to
-	  support PC/104 devices on X86_64 platforms.
+	  Expose ISA bus device drivers and options available for selection and
+	  configuration. Enable this option if your target machine has an ISA
+	  bus. ISA is an older system, displaced by PCI and newer bus
+	  architectures -- if your target machine is modern, it probably does
+	  not have an ISA bus.
 
 	  If unsure, say N.