Either way, it needs changing.
Let's see if someone actually tests the code first though.
I've taken the liberty of bulding it, but I don't have the h/w to actually run the code.
I get: drivers/mfd/mc13xxx-spi.c: In function ‘mc13xxx_spi_write’: drivers/mfd/mc13xxx-spi.c:97:14: warning: initialisation discards ‘const’ qualifier from pointer target type [enabled by default]