staging: rtl8712: Replace function r8712_init_cmd_priv()

Remove function r8712_init_cmd_priv as all it does is call
_init_cmd_priv.
Rename _init_cmd_priv to r8712_init_cmd_priv to maintain compatibility
with call sites.
Change type of new r8712_init_cmd_priv from static to non-static as
original r8712_init_cmd_priv was non-static.
Change return type of new r8712_init_cmd_priv to int as original had
return type u32 but new (formerly _init_cmd_priv) had return type sint.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>