Convert CONFIG_BOOTP_SEND_HOSTNAME to Kconfig

This converts the following to Kconfig:
   CONFIG_BOOTP_SEND_HOSTNAME

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/devkit8000_defconfig b/configs/devkit8000_defconfig
index 593e9ca..bd20c43 100644
--- a/configs/devkit8000_defconfig
+++ b/configs/devkit8000_defconfig
@@ -33,6 +33,7 @@
 CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_BOOTP_SEND_HOSTNAME=y
 CONFIG_TWL4030_LED=y
 CONFIG_MMC_OMAP_HS=y
 CONFIG_MTD=y