Enable I2C Alternate Function Remapping

This adds support for using I2C with the alternate mappings PD1, PD0 and PC5, PC6.

To use PD1 (the SWDIO pin), pinV32_DisconnectDebug(PD_1) must be called before Wire.begin(), not sure if this should be documented somewhere or added to the code?

I also changed the existing default mapping to use AFIO_Remap_I2C1_DISABLE so that it is possible to change the pin mapping back to the default at runtime.

Tested on CHV0003F4P6-EVT-R0.
Source openwch/arduino_core_ch32#152

Author: jobitjoseph

variants/CH32V00x/CH32V003F4/PeripheralPins.c

@@ -47,14 +47,18 @@ WEAK const PinMap PinMap_ADC[] = {
 //*** I2C ***
 #ifdef I2C_MODULE_ENABLED
 WEAK const PinMap PinMap_I2C_SDA[] = {
-  {PC_1, I2C1, CH_PIN_DATA(CH_MODE_OUTPUT_50MHz, CH_CNF_OUTPUT_AFOD, NOPULL, AFIO_NONE)},
+  {PC_1, I2C1, CH_PIN_DATA(CH_MODE_OUTPUT_50MHz, CH_CNF_OUTPUT_AFOD, NOPULL, AFIO_Remap_I2C1_DISABLE)},
+  {PD_0, I2C1, CH_PIN_DATA(CH_MODE_OUTPUT_50MHz, CH_CNF_OUTPUT_AFOD, NOPULL, AFIO_PartialRemap_I2C1_ENABLE)},
+  {PC_6, I2C1, CH_PIN_DATA(CH_MODE_OUTPUT_50MHz, CH_CNF_OUTPUT_AFOD, NOPULL, AFIO_FullRemap_I2C1_ENABLE)},
   {NC,   NP,   0}
 };
 #endif
 
 #ifdef I2C_MODULE_ENABLED
 WEAK const PinMap PinMap_I2C_SCL[] = {
-  {PC_2, I2C1, CH_PIN_DATA(CH_MODE_OUTPUT_50MHz, CH_CNF_OUTPUT_AFOD, NOPULL, AFIO_NONE)},
+  {PC_2, I2C1, CH_PIN_DATA(CH_MODE_OUTPUT_50MHz, CH_CNF_OUTPUT_AFOD, NOPULL, AFIO_Remap_I2C1_DISABLE)},
+  {PD_1, I2C1, CH_PIN_DATA(CH_MODE_OUTPUT_50MHz, CH_CNF_OUTPUT_AFOD, NOPULL, AFIO_PartialRemap_I2C1_ENABLE)},
+  {PC_5, I2C1, CH_PIN_DATA(CH_MODE_OUTPUT_50MHz, CH_CNF_OUTPUT_AFOD, NOPULL, AFIO_FullRemap_I2C1_ENABLE)},
   {NC,   NP,   0}
 };
 #endif