Convert CONFIG_AT91_GPIO_PULLUP to Kconfig

This converts the following to Kconfig:
   CONFIG_AT91_GPIO_PULLUP

Cc: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/mach-at91/Kconfig b/arch/arm/mach-at91/Kconfig
index e99b906..79fe87c 100644
--- a/arch/arm/mach-at91/Kconfig
+++ b/arch/arm/mach-at91/Kconfig
@@ -311,6 +311,10 @@
 	  Enable the driver for the embedded flash used in the Atmel
 	  AT91SAM9XE devices.
 
+config AT91_GPIO_PULLUP
+	bool "Keep pullups on peripheral pins"
+	depends on CPU_ARM926EJS
+
 source "board/atmel/at91sam9260ek/Kconfig"
 source "board/atmel/at91sam9261ek/Kconfig"
 source "board/atmel/at91sam9263ek/Kconfig"