Blackfin arch: add some missing syscall

When compiling the Blackfin kernel, checksyscalls.pl will report lots of missing syscalls warnings.
This patch will add some missing syscalls which make sense on Blackfin arch

After appling this patch, toolchain should be rebuilt. Then recompiling the kernel with the new
toolchain.

Signed-off-by: Bryan Wu <bryan.wu@analog.com>