spi: Make max_tx and max_rx the same type
spi: Make max_tx and max_rx the same type

Prevents spurious compiler warnings.

Signed-off-by: Mark Brown <b51b9a92386687a9ac927cebfa0f978adeb8cea5@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs