[MTD] dataflash OTP support

Now that we can tell when we have one of the newer DataFlash chips,
optionally expose the 128 bytes of OTP memory they provide.  Tested
on at45db642 revision B and D chips.

Switch mtdchar over to a generic HAVE_MTD_OTP flag instead of adding
another #ifdef for each type of chip whose driver has OTP support.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Bryan Wu <cooloney@kernel.org>
Cc: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/onenand/Kconfig b/drivers/mtd/onenand/Kconfig
index cb41cbc..b94a61b 100644
--- a/drivers/mtd/onenand/Kconfig
+++ b/drivers/mtd/onenand/Kconfig
@@ -29,6 +29,7 @@
 
 config MTD_ONENAND_OTP
 	bool "OneNAND OTP Support"
+	select HAVE_MTD_OTP
 	help
 	  One Block of the NAND Flash Array memory is reserved as
 	  a One-Time Programmable Block memory area.