rp2/machine_pin: Move decl of machine_pin_obj_table to public header.

So other code can include `machine_pin.h` and use the pin name macros such
as `pin_GPIO0`.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

ports/rp2/machine_pin.c

@@ -86,7 +86,6 @@ typedef struct _machine_pin_irq_obj_t {
 } machine_pin_irq_obj_t;
 
 static const mp_irq_methods_t machine_pin_irq_methods;
-extern const machine_pin_obj_t machine_pin_obj_table[NUM_BANK0_GPIOS];
 
 // Mask with "1" indicating that the corresponding pin is in simulated open-drain mode.
 uint64_t machine_pin_open_drain_mask;

ports/rp2/machine_pin.h

@@ -64,6 +64,8 @@ extern const mp_obj_type_t machine_pin_af_type;
 // Include all of the individual pin objects
 #include "genhdr/pins.h"
 
+extern const machine_pin_obj_t machine_pin_obj_table[NUM_BANK0_GPIOS];
+
 extern const mp_obj_type_t pin_cpu_pins_obj_type;
 extern const mp_obj_dict_t machine_pin_cpu_pins_locals_dict;