can: mcp251xfd: mcp251xfd_get_timestamp(): move to mcp251xfd.h

This is a preparation patch, it moves the mcp251xfd_get_timestamp()
function into the mcp251xfd.h file.

Link: https://lore.kernel.org/r/20210304160328.2752293-5-mkl@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c

@@ -1597,12 +1597,6 @@ static int mcp251xfd_handle_rxif(struct mcp251xfd_priv *priv)
 	return 0;
 }
 
-static inline int mcp251xfd_get_timestamp(const struct mcp251xfd_priv *priv,
-					  u32 *timestamp)
-{
-	return regmap_read(priv->map_reg, MCP251XFD_REG_TBC, timestamp);
-}
-
 static struct sk_buff *
 mcp251xfd_alloc_can_err_skb(const struct mcp251xfd_priv *priv,
 			    struct can_frame **cf, u32 *timestamp)

drivers/net/can/spi/mcp251xfd/mcp251xfd.h

@@ -728,6 +728,12 @@ mcp251xfd_spi_cmd_write(const struct mcp251xfd_priv *priv,
 	return data;
 }
 
+static inline int mcp251xfd_get_timestamp(const struct mcp251xfd_priv *priv,
+					  u32 *timestamp)
+{
+	return regmap_read(priv->map_reg, MCP251XFD_REG_TBC, timestamp);
+}
+
 static inline u16 mcp251xfd_get_tef_obj_addr(u8 n)
 {
 	return MCP251XFD_RAM_START +