arch/lm32/ram.ld: provide mprintf if missing

When we'll enable pp_printf, we'll need to resolve mprintf to
it. Local files are fixed by #define in wrc.h, but ptp-noposix has
explicit mprintf calls inside.  By using "PROVIDE" in the linker
script, we resolve mprintf to pp_printf only if no native mprintf
is part of the link stage. This has no effect if pp_printf is
not selected.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

arch/lm32/ram.ld

@@ -57,3 +57,6 @@ SECTIONS
 	/* First location in stack is highest address in RAM */
 	PROVIDE(_fstack = ORIGIN(ram) + LENGTH(ram) - 4);
 }
+
+/* We need to provide mprintf to ptp-noposix object files, if missing */
+PROVIDE(mprintf = pp_printf);