CONFIG_SYS_CLK_FREQ: Consistently be static or get_board_sys_clk()

This CONFIG option is used in one of two ways.  The first way is that it
is defined to a static value, of an unsigned long size.  The second way
is that it is defined to something, typically a function, to determine
this value at run time.

However, in a few cases that function returns a static value.  Change
that to using the static value directly.

In the case of using something at run time, convert everything to using
a function of the same name and prototype.  This will allow for further
cleanups.

Finally, we have a few cases where the function is just not used, so
drop it.

Signed-off-by: Tom Rini <trini@konsulko.com>

include/configs/xtfpga.h

@@ -23,7 +23,10 @@
 #define CONFIG_XTFPGA
 
 /* FPGA CPU freq after init */
-#define CONFIG_SYS_CLK_FREQ		(gd->cpu_clk)
+#ifndef __ASSEMBLY__
+unsigned long get_board_sys_clk(void);
+#endif
+#define CONFIG_SYS_CLK_FREQ		get_board_sys_clk()
 
 /*===================*/
 /* RAM Layout        */