linux-user/syscall: Constify bitmask_transtbl fcntl/mmap flags_tlb[]

Keep bitmask_transtbl in .rodata by marking the arrays const.

Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210517055243.830491-1-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>