rockchip: defconfig: puma-rk3399: enable SPL_BOARD_INIT

For the RK3399-Q7, we need spl_board_init to be called during SPL
startup to set up the pinmux for the debug UART. Enable SPL_BOARD_INIT
via defconfig to ensure this function is in fact called.
Signed-off-by: NPhilipp Tomsich <philipp.tomsich@theobroma-systems.com>

configs/puma-rk3399_defconfig

@@ -14,6 +14,7 @@ CONFIG_FIT=y
 CONFIG_SPL_LOAD_FIT=y
 CONFIG_SPL_FIT_SOURCE="board/theobroma-systems/puma_rk3399/fit_spl_atf.its"
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_SPL_BOARD_INIT=y
 # CONFIG_SPL_RAW_IMAGE_SUPPORT is not set
 # CONFIG_SPL_LEGACY_IMAGE_SUPPORT is not set
 CONFIG_SPL_STACK_R=y