The existing code assumed that PL011_DMA_BUFFER_SIZE == UART_XMIT_SIZE,
which may not always be the case.  This allows for these two being
different sizes and not copying too much data.
Signed-off-by: NAndrew Jackson <Andrew.Jackson@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>