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>
diff --git a/board/freescale/ls1088a/ls1088a.c b/board/freescale/ls1088a/ls1088a.c
index 73c2077..8a112a6 100644
--- a/board/freescale/ls1088a/ls1088a.c
+++ b/board/freescale/ls1088a/ls1088a.c
@@ -374,6 +374,7 @@
 #endif
 }
 
+#ifdef CONFIG_DYNAMIC_SYS_CLK_FREQ
 unsigned long get_board_sys_clk(void)
 {
 	u8 sysclk_conf = QIXIS_READ(brdcfg[1]);
@@ -397,6 +398,7 @@
 
 	return 66666666;
 }
+#endif
 
 #ifdef CONFIG_DYNAMIC_DDR_CLK_FREQ
 unsigned long get_board_ddr_clk(void)