spi: Remove used spi_init

spi_init used in some areas in tree, but the respective
drivers will remove in future patches.

So remove the same instances.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>

examples/standalone/atmel_df_pow2.c

@@ -126,8 +126,6 @@ int atmel_df_pow2(int argc, char * const argv[])
 		return 1;
 	}
 
-	spi_init();
-
 	while (1) {
 		struct spi_slave *slave;
 		char *line, *p;