sunxi: Silence warning about non-static inline function

When compiling with CONFIG_SPL_SERIAL=n, gcc warns about
mbus_configure_port not being marked as static:

In file included from include/common.h:34,
                 from arch/arm/mach-sunxi/dram_sunxi_dw.c:11:
include/log.h:185:4: warning: 'printf' is static but used in inline function 'mbus_configure_port' which is not static
  185 |    printf(pr_fmt(fmt), ##args); \
      |    ^~~~~~
include/log.h:192:2: note: in expansion of macro 'debug_cond'
  192 |  debug_cond(_DEBUG, fmt, ##args)
      |  ^~~~~~~~~~
arch/arm/mach-sunxi/dram_sunxi_dw.c:100:2: note: in expansion of macro 'debug'
  100 |  debug("MBUS port %d cfg0 %08x cfg1 %08x\n", port, cfg0, cfg1);
      |  ^~~~~

Fix this by updating the function accordingly.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>