char: cadence_uart: Clean up variable names

char: cadence_uart: Clean up variable names

Clean up some variable names in preparation for migrating the state struct
and type cast macro to a public header. The acronym "UART" on it's own is
not specific enough to be used in a more global namespace so preface with
"cadence". Fix the capitalisation of "uart" in the state type while touching
the typename. Preface macros used by the state struct itself with CADENCE_UART
so they don't conflict in namespace either.

Reviewed-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Tested-by: Alistair Francis <alistair.francis@xilinx.com>
Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 3812b7426c338beae9e082557f3524a99310ddc6.1431381507.git.peter.crosthwaite@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>