arm: zynq: Move ps7_* to separate file

Extract ps7_* from spl code to prepare for extension.
And also return value.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/mach-zynq/Makefile b/arch/arm/mach-zynq/Makefile
index bf29b4d..e3f0117 100644
--- a/arch/arm/mach-zynq/Makefile
+++ b/arch/arm/mach-zynq/Makefile
@@ -15,4 +15,4 @@
 obj-y	+= clk.o
 obj-y	+= lowlevel_init.o
 AFLAGS_lowlevel_init.o := -mfpu=neon
-obj-$(CONFIG_SPL_BUILD)	+= spl.o
+obj-$(CONFIG_SPL_BUILD)	+= spl.o ps7_spl_init.o