staging: lustre: clean function declaration in super25.c up

We get 1 warning when building kernel with W=1:
drivers/staging/lustre/lnet/selftest/conctl.c:804:1: warning: no previous prototype for 'lstcon_ioctl_entry' [-Wmissing-prototypes]

In fact, this function is declared in
drivers/staging/lustre/lustre/llite/super25.c, but should be
moved into a header file, thus can be recognized in other file.

So this patch moves the declaration into
drivers/staging/lustre/lnet/selftest/console.h

Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>