Fix compiler warning:

In file included from sketch/BlinkM.cpp:5:0:
sketch/Marlin.h:422:13: warning: 'void print_time_remaining_init()' declared 'static' but never defined [-Wunused-function]
 static void print_time_remaining_init();

Make local functions static. Saves 6B of flash.

Firmware/Marlin.h

@@ -419,7 +419,6 @@ extern void fsensor_init();
 //estimated time to end of the print
 extern uint16_t print_time_remaining();
 extern uint8_t print_percent_done();
-static void print_time_remaining_init();
 
 #ifdef HOST_KEEPALIVE_FEATURE
 

Firmware/Marlin_main.cpp

@@ -535,8 +535,9 @@ static bool saved_extruder_relative_mode = false;
 //=============================Routines======================================
 //===========================================================================
 
-void get_arc_coordinates();
-bool setTargetedHotend(int code);
+static void get_arc_coordinates();
+static bool setTargetedHotend(int code);
+static void print_time_remaining_init();
 
 void serial_echopair_P(const char *s_P, float v)
     { serialprintPGM(s_P); SERIAL_ECHO(v); }