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/chiliboard_defconfig b/configs/chiliboard_defconfig
index 9c3fe8e..51dc1a7 100644
--- a/configs/chiliboard_defconfig
+++ b/configs/chiliboard_defconfig
@@ -45,6 +45,7 @@
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_BOOTP_SEND_HOSTNAME=y
 CONFIG_BOOTCOUNT_LIMIT=y
 CONFIG_MISC=y
 CONFIG_DM_MMC=y