lib: move GENERIC_IOMAP to lib/Kconfig

define GENERIC_IOMAP in a central location
instead of all architectures. This will be helpful
for the follow-up patch which makes it select
other configs. Code is also a bit shorter this way.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
index 02513c2..9059e39 100644
--- a/arch/hexagon/Kconfig
+++ b/arch/hexagon/Kconfig
@@ -26,6 +26,7 @@
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_TRACEHOOK
 	select NO_IOPORT
+	select GENERIC_IOMAP
 	# mostly generic routines, with some accelerated ones
 	---help---
 	  Qualcomm Hexagon is a processor architecture designed for high
@@ -73,9 +74,6 @@
 config GENERIC_IRQ_PROBE
 	def_bool y
 
-config GENERIC_IOMAP
-	def_bool y
-
 #config ZONE_DMA
 #	bool
 #	default y