Convert CONFIG_HWCONFIG to Kconfig

This converts the following to Kconfig:
   CONFIG_HWCONFIG

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/kontron_sl28_defconfig b/configs/kontron_sl28_defconfig
index f044334..9b90ed4 100644
--- a/configs/kontron_sl28_defconfig
+++ b/configs/kontron_sl28_defconfig
@@ -39,6 +39,7 @@
 CONFIG_BOOTDELAY=10
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOARD_LATE_INIT=y
+# CONFIG_HWCONFIG is not set
 CONFIG_PCI_INIT_R=y
 CONFIG_SPL_MAX_SIZE=0x20000
 CONFIG_SPL_HAS_BSS_LINKER_SECTION=y