arm: freescale: Rename initdram() to fsl_initdram()

This function name shadows a global name but is in fact different. This
is very confusing. Rename it to help with the following refactoring.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/freescale/ls1021aqds/ddr.c b/board/freescale/ls1021aqds/ddr.c
index 3bf2e49..d16a69f 100644
--- a/board/freescale/ls1021aqds/ddr.c
+++ b/board/freescale/ls1021aqds/ddr.c
@@ -164,7 +164,7 @@
 }
 #endif
 
-int initdram(void)
+int fsl_initdram(void)
 {
 	phys_size_t dram_size;