extmod/modmachine: Factor ports' machine module dict to common code.

This is a code factoring to have the dict for the machine module in one
location, and all the ports use that same dict.  The machine.soft_reset()
function implementation is also factored because it's the same for all
ports that did already implement it.  Eventually more functions/bindings
can be factored.

All ports remain functionally the same, except:
- cc3200 port: gains soft_reset, mem8, mem16, mem32, Signal; loses POWER_ON
  (which was a legacy constant, replaced long ago by PWRON_RESET)
- nrf port: gains Signal
- qemu-arm port: gains soft_reset
- unix port: gains soft_reset
- zephyr port: gains soft_reset, mem8, mem16, mem32

Signed-off-by: Damien George <damien@micropython.org>
diff --git a/ports/esp32/mpconfigport.h b/ports/esp32/mpconfigport.h
index 706baae..8a21cab 100644
--- a/ports/esp32/mpconfigport.h
+++ b/ports/esp32/mpconfigport.h
@@ -96,6 +96,7 @@
 #define MICROPY_PY_OS_UNAME                 (1)
 #define MICROPY_PY_OS_URANDOM               (1)
 #define MICROPY_PY_MACHINE                  (1)
+#define MICROPY_PY_MACHINE_INCLUDEFILE      "ports/esp32/modmachine.c"
 #define MICROPY_PY_MACHINE_ADC              (1)
 #define MICROPY_PY_MACHINE_ADC_INCLUDEFILE  "ports/esp32/machine_adc.c"
 #define MICROPY_PY_MACHINE_ADC_ATTEN_WIDTH  (1)
@@ -106,6 +107,7 @@
 #define MICROPY_PY_MACHINE_ADC_BLOCK_INCLUDEFILE "ports/esp32/machine_adc_block.c"
 #define MICROPY_PY_MACHINE_PIN_MAKE_NEW     mp_pin_make_new
 #define MICROPY_PY_MACHINE_BITSTREAM        (1)
+#define MICROPY_PY_MACHINE_DHT_READINTO     (1)
 #define MICROPY_PY_MACHINE_PULSE            (1)
 #define MICROPY_PY_MACHINE_PWM              (1)
 #define MICROPY_PY_MACHINE_PWM_DUTY         (1)