tty: serial: samsung: constify variables and pointers

Constify variables, data pointed by several pointers and
"udivslot_table" static array.  This makes code a bit safer.

Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20220308080919.152715-8-krzysztof.kozlowski@canonical.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>