spi: Don't break user-visible strings to multiple source lines in drivers

User-visible strings are more difficult to grep from sources if they are
separated to multiple source lines. This is worse than over 80 columns long
line code style violation.

Fix this by making those to single-line strings or by breaking them between
variables.

While at there, convert if (printk_ratelimit()) dev_warn() to use
dev_warn_ratelimited in spi-pxa2xx.c.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>