linux-user: Add missing Mips syscalls items in strace.list

Without this patch, a number of Mips syscalls will be logged in the following
way (in this example, this is an invocation of accept4()):

  86906 Unknown syscall 4334

This patch provides standard Qemu's strace output for such cases, like this:

  95861 accept4(3,1996486000,1996486016,128,0,0) = 5

Such output may be further improved by providing strace-related functions
that handle only particular syscalls, but this is beyond the scope of
this patch.

Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Acked-by: Riku Voipio <riku.voipio@linaro.org>
Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>