linux-user: correct argument number for sys_mremap and sys_splice
sys_mremap missed 5th argument (new_address), which caused examples that
remap to a specific address to fail.
sys_splice missed 5th and 6th argument which caused different examples to
fail.
This change has an effect on MIPS target only.
Signed-off-by: Petar Jovanovic <petar.jovanovic@imgtec.com> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>