tty: serial: simplify qcom_geni_serial_send_chunk_fifo()

* use memcpy() instead of the loop (removes c variable)
* use remaining parameter directly (removes chunk variable)

The code is simpler and easier to follow.

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: linux-arm-msm@vger.kernel.org
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230420093514.13055-1-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>