p54spi: fix p54spi_upload_firmware

Instead of firmware itself p54_upload_firmware was sending to the device
content of struct firmware and the following random garbage.

Notice '&' before priv->firmware->data at p54spi_spi_write.
But simple removing of '&' sign triggered BUG_ON at dma_cache_maint.
Thus kmemdup - kfree workaround.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>