Start split out of common open firmware code

This creates drivers/of/base.c (depending on CONFIG_OF) and puts
the first trivially common bits from the prom.c files into it.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Paul Mackerras <paulus@samba.org>
Acked-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/Makefile b/drivers/Makefile
index 0ea8e32..a9e4c5f 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -86,3 +86,4 @@
 obj-$(CONFIG_DMA_ENGINE)	+= dma/
 obj-$(CONFIG_HID)		+= hid/
 obj-$(CONFIG_PPC_PS3)		+= ps3/
+obj-$(CONFIG_OF)		+= of/