viafb: package often used basic io functions

This patch puts redesigned versions of the basic io functions that
are used overall the driver in an extra header. It is prefixed with
via_ as no framebuffer dependend stuff is in there. They were inlined
as they are really simple which reduced the module size about 2.5%.
The parameter order of read and write was fixed as it really doesn't
make sense to change the order as they are parts of the same address
and not source and destination.
Wrapper which use the new functions were added to hw.h to replicate
the old interface and avoid changing all old code.

[jc: added one comment]
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>