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/configs/snapper9260_defconfig b/configs/snapper9260_defconfig
index c204915..69b73c9 100644
--- a/configs/snapper9260_defconfig
+++ b/configs/snapper9260_defconfig
@@ -5,6 +5,7 @@
 CONFIG_SYS_TEXT_BASE=0x21f00000
 CONFIG_SYS_MALLOC_LEN=0x100000
 CONFIG_TARGET_SNAPPER9260=y
+CONFIG_AT91_GPIO_PULLUP=y
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ENV_SIZE=0x40000
 CONFIG_ENV_OFFSET=0x80000