sh: Add syscall entries for non multiplexed socket calls

Linux kernel already has socket syscalls that can be invoked
without the multiplexing sys_socketcall wrapper.
C library wrappers are ready to use them directly. It needs just
to define the missing syscall numbers and provide the related entries
into the syscalls table, like sh64 aleady does.

Signed-off-by: Francesco Rundo <francesco.rundo@st.com>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>