arm: socfpga: scan: Staticize scan_mgr_io_scan_chain_prg()

This function is never used outside of scan_manager.c , so make it static.
Zap the prototype in scan_manager.h and move the documentation above the
function. Make the documentation kerneldoc compliant.

Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/arch/arm/mach-socfpga/scan_manager.c b/arch/arm/mach-socfpga/scan_manager.c
index a820b1b..ab7aaec 100644
--- a/arch/arm/mach-socfpga/scan_manager.c
+++ b/arch/arm/mach-socfpga/scan_manager.c
@@ -38,11 +38,15 @@
 	return 1;
 }
 
-/* Program HPS IO Scan Chain */
-uint32_t scan_mgr_io_scan_chain_prg(
-	uint32_t io_scan_chain_id,
-	uint32_t io_scan_chain_len_in_bits,
-	const uint32_t *iocsr_scan_chain)
+/**
+ * scan_mgr_io_scan_chain_prg() - Program HPS IO Scan Chain
+ * @io_scan_chain_id:		IO scan chain ID
+ * @io_scan_chain_len_in_bits:	IO scan chain length in bits
+ * @iocsr_scan_chain:		IO scan chain table
+ */
+static int scan_mgr_io_scan_chain_prg(const unsigned int io_scan_chain_id,
+				      uint32_t io_scan_chain_len_in_bits,
+				      const uint32_t *iocsr_scan_chain)
 {
 	uint16_t tdi_tdo_header;
 	uint32_t io_program_iter;