usb: sisusb_con, convert addr macros to functions

Convert SISUSB_VADDR and SISUSB_HADDR to inline functions. Now, there
are no more hidden accesses to local variables (vc_data and
sisusb_usb_data).

sisusb_haddr returns unsigned long from now on, not u16 *, as ulong is
what every caller expects -- we can remove some casts.

Call sites were aligned to be readable too.

Use sisusb_haddr on 4 more places in sisusbcon_blank and
sisusbcon_scroll. It was open coded there with [x, y] being [0, 0].

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>