arm: am437x: cm-t43: fix cm-t43 boot

spl_board_init() is necessary for boot. Remove the #undef that keeps
it out of the boot sequence.

Cc: Tom Rini <trini@konsulko.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Reviewed-by: Tom Rini <trini@konsulko.com>

include/configs/cm_t43.h

@@ -98,7 +98,6 @@
 #undef CONFIG_SPL_OS_BOOT
 #undef CONFIG_SPL_GPIO_SUPPORT
 #undef CONFIG_SPL_NAND_SUPPORT
-#undef CONFIG_SPL_BOARD_INIT
 #undef CONFIG_BOOTDELAY
 #include <config_distro_defaults.h>
 #define CONFIG_ZERO_BOOTDELAY_CHECK