mmc: mmc_spi: Join string literals back

For easy grepping on debug purposes join string literals back in
the messages.

No functional change.

While here, join list of module authors as well.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>