common/board_f.c: change the macro name and remove it for PPC platforms

For most PPC platforms, they will call the first get_clocks() in
init_sequence_f[] as they define CONFIG_PPC. CONFIG_SYS_FSL_CLK is
then defined to call the second get_clocks(), which should be
redundant for PPC.

Signed-off-by: Gong Qianyu <Qianyu.Gong@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>
diff --git a/doc/README.fsl-clk b/doc/README.fsl-clk
new file mode 100644
index 0000000..9e83c24
--- /dev/null
+++ b/doc/README.fsl-clk
@@ -0,0 +1,6 @@
+Freescale system clock options
+
+	- CONFIG_SYS_FSL_CLK
+		Enable to call get_clocks() in board_init_f() for
+		non-PPC platforms and PCC 8xx platforms such as
+		TQM866M and TQM885D.