configs: Migrate CONFIG_SYS_LDSCRIPT to Kconfig

In order to migrate this symbol to Kconfig introduce a new symbol to
guard it, CONFIG_SYS_CUSTOM_LDSCRIPT.  When that is set we can then
provide the exact final location o the script.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/zynq_picozed_defconfig b/configs/zynq_picozed_defconfig
index 0650ce2..453cd54 100644
--- a/configs/zynq_picozed_defconfig
+++ b/configs/zynq_picozed_defconfig
@@ -5,6 +5,8 @@
 CONFIG_SPL_STACK_R_ADDR=0x200000
 CONFIG_SPL=y
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_SYS_CUSTOM_LDSCRIPT=y
+CONFIG_SYS_LDSCRIPT="arch/arm/mach-zynq/u-boot.lds"
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SYS_PROMPT="Zynq> "