mfd: arizona-spi: Add lines after declarations - checkpatch catch

This was found whilst running checkpatch.pl on arizona-spi.

WARNING: Missing a blank line after declarations
+       struct arizona *arizona = spi_get_drvdata(spi);
+       arizona_dev_exit(arizona);

Signed-off-by: Will Sheppard <wsheppard@embedded-bits.co.uk>
Signed-off-by: Lee Jones <lee.jones@linaro.org>