spi: move common spi_setup() functionality into core

Start moving some spi_setup() functionality into the SPI core from the
various spi_master controller drivers:

 - Make that function stop being an inline;

 - Move two common idioms from drivers into that new function:
    * Default bits_per_word to 8 if that field isn't set
    * Issue a standardized dev_dbg() message

This is a net minor source code shrink, and supports enhancments found in
some follow-up patches.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/spi/spi_imx.c b/drivers/spi/spi_imx.c
index 0671aee..26d5ef0 100644
--- a/drivers/spi/spi_imx.c
+++ b/drivers/spi/spi_imx.c
@@ -1286,10 +1286,7 @@
 
 	/* SPI word width */
 	tmp = spi->bits_per_word;
-	if (tmp == 0) {
-		tmp = 8;
-		spi->bits_per_word = 8;
-	} else if (tmp > 16) {
+	if (tmp > 16) {
 		status = -EINVAL;
 		dev_err(&spi->dev,
 			"setup - "