target/mips: Remove access_type argument from get_physical_address()

get_physical_address() doesn't use the 'access_type' argument,
remove it to simplify.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-Id: <20210128144125.3696119-5-f4bug@amsat.org>