sunxi: compile clock.c for SPL only

With the clock_twi_onoff() function now being called only from the SPL,
the whole clock.c file in arch/arm/mach-sunxi is needed by SPL code
only.

Remove the redundant #ifdef from the clock_init() function, actually
this function was already only called from the SPL.
Then adjust the Makefile to compile clock.c only with CONFIG_SPL_BUILD
defined.

This avoids unnecessary code in U-Boot proper and allows further
refactoring and code-split between the SPL and U-Boot proper.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>

arch/arm/mach-sunxi/Makefile

@@ -7,7 +7,6 @@
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 
 obj-y	+= board.o
-obj-y	+= clock.o
 obj-y	+= cpu_info.o
 obj-y	+= dram_helpers.o
 obj-$(CONFIG_SUN6I_PRCM)	+= prcm.o
@@ -31,6 +30,7 @@ obj-y	+= timer.o
 endif
 
 ifdef CONFIG_SPL_BUILD
+obj-y				+= clock.o
 obj-$(CONFIG_MACH_SUNIV)	+= dram_suniv.o
 obj-$(CONFIG_DRAM_SUN4I)	+= dram_sun4i.o
 obj-$(CONFIG_DRAM_SUN6I)	+= dram_sun6i.o

arch/arm/mach-sunxi/clock.c

@@ -23,10 +23,8 @@ __weak void gtbus_init(void)
 
 int clock_init(void)
 {
-#ifdef CONFIG_SPL_BUILD
 	clock_init_safe();
 	gtbus_init();
-#endif
 	clock_init_uart();
 	clock_init_sec();