arm64: Enable INIT_SP_RELATIVE by default when POC is enabled

When position-independent pre-relocation code is enable there is also
necessary to enable relative early stack pointer not to use origin location
pointed by CONFIG_SYS_INIT_SP_ADDR macro.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 8f95077..528a7ce 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -12,6 +12,7 @@
 if ARM64
 config POSITION_INDEPENDENT
 	bool "Generate position-independent pre-relocation code"
+	select INIT_SP_RELATIVE
 	help
 	  U-Boot expects to be linked to a specific hard-coded address, and to
 	  be loaded to and run from that address. This option lifts that