NFC: qca199x: use coherent memory for i2c read

I2C dma reads returned garbage on large reads for 64 bit systems. We
allocate coherent memory that persists for the life of the driver and
use it to buffer the dma access before coppying the data back out to
userspace.

Change-Id: I9369007f3ccc2904ef939b5e3d5934538bbd0b4d
Signed-off-by: Houston Hoffman <hhoffman@codeaurora.org>