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/da850evm_nand_defconfig b/configs/da850evm_nand_defconfig
index 9555dd3..d6e2a0a 100644
--- a/configs/da850evm_nand_defconfig
+++ b/configs/da850evm_nand_defconfig
@@ -69,6 +69,7 @@
 CONFIG_SYS_NAND_USE_FLASH_BBT=y
 CONFIG_NAND_DAVINCI=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_SYS_NAND_U_BOOT_LOCATIONS=y