Convert CONFIG_SYS_NAND_PAGE_COUNT to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_NAND_PAGE_COUNT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/smartweb_defconfig b/configs/smartweb_defconfig
index 187a001..bc0d9c0 100644
--- a/configs/smartweb_defconfig
+++ b/configs/smartweb_defconfig
@@ -64,6 +64,7 @@
 # CONFIG_SYS_NAND_USE_FLASH_BBT is not set
 CONFIG_NAND_ATMEL=y
 CONFIG_SYS_NAND_BLOCK_SIZE=0x20000
+CONFIG_SYS_NAND_PAGE_COUNT=0x40
 CONFIG_SYS_NAND_PAGE_SIZE=0x800
 CONFIG_SYS_NAND_OOBSIZE=0x40
 CONFIG_PHYLIB=y