sunxi: dram: make MBUS configuration functions static

The usage of the C keyword "inline" seems to be a common
misunderstanding: it's a *hint* only, and modern compilers will inline
(or not) functions based on their own judgement and provided compiler
options.
So while marking functions as "inline" does not do much, missing the
"static" keyword will force to compiler to spell out a version of the
function for potential external callers, which actually increases the
code size (though hopefully the linker will drop the function).

Change the "inline" attribute for the mbus_configure_port() functions in
some Allwinner DRAM drivers to "static", so that the explicit version
can actually be dropped from the object file, reducing the code size.

"static inline" has a use case in header files, where it avoids a warning
if a .c file including this header does not use the particular function.
In a .c file itself "static inline" is not useful otherwise, so just use
static here as well.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>