rockchip: rk3399: Fix TPL build of bob and kevin

Building chromebook_bob/kevin with TPL=y ends with a linking error:

  arch/arm/mach-rockchip/rk3399/rk3399.o: in function `board_debug_uart_init':
  arch/arm/mach-rockchip/rk3399/rk3399.c:148:(.text.board_debug_uart_init+0x34):
    undefined reference to `spl_gpio_output'
  arch/arm/mach-rockchip/rk3399/rk3399.c:148:(.text.board_debug_uart_init+0x34):
    relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `spl_gpio_output'

  make[2]: *** [scripts/Makefile.xpl:542: tpl/u-boot-tpl] Error 1
  make[1]: *** [Makefile:2134: tpl/u-boot-tpl] Error 2
  make: *** [Makefile:568: __build_one_by_one] Error 2

Change to only use spl_gpio functions in SPL to fix this.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/rk3399/rk3399.c b/arch/arm/mach-rockchip/rk3399/rk3399.c
index 0c28241..ba89079 100644
--- a/arch/arm/mach-rockchip/rk3399/rk3399.c
+++ b/arch/arm/mach-rockchip/rk3399/rk3399.c
@@ -136,7 +136,7 @@
 	struct rk3399_pmugrf_regs * const pmugrf = (void *)PMUGRF_BASE;
 	struct rockchip_gpio_regs * const gpio = (void *)GPIO0_BASE;
 
-	if (IS_ENABLED(CONFIG_XPL_BUILD) &&
+	if (IS_ENABLED(CONFIG_SPL_BUILD) &&
 	    (IS_ENABLED(CONFIG_TARGET_CHROMEBOOK_BOB) ||
 	     IS_ENABLED(CONFIG_TARGET_CHROMEBOOK_KEVIN))) {
 		rk_setreg(&grf->io_vsel, 1 << 0);