Use explicitly sized types from stdint

Replace bare int types with stdint types. This was done with:

    grep -rwl 'int' src/ | xargs sed -i 's/\<int\>/int16_t/g'
    grep -rwl 'unsigned long' src/ | xargs sed -i 's/\<unsigned long\>/uint32_t/g'
    grep -rwl 'unsigned char' src/ | xargs sed -i 's/\<unsigned char\>/uint8_t/g'

Then reverted for *main(), putchar(), and getchar().

The Arduino declarations for parallel_main() were also corrected to
match their definitions.

SDCC does *not* generate the same code in all instances, due to `int`
being treated different than `short int`.

Signed-off-by: Tim Crawford <tcrawford@system76.com>

src/board/system76/common/dgpu.c

@@ -66,7 +66,7 @@ uint8_t dgpu_get_fan_duty(void) {
     if (power_state == POWER_STATE_S0 && gpio_get(&DGPU_PWR_EN) && !gpio_get(&GC6_FB_EN)) {
         // Use I2CS if in S0 state
         int8_t rlts;
-        int res = i2c_get(&I2C_DGPU, 0x4F, 0x00, &rlts, 1);
+        int16_t res = i2c_get(&I2C_DGPU, 0x4F, 0x00, &rlts, 1);
         if (res == 1) {
             dgpu_temp = (int16_t)rlts;
             duty = fan_duty(&FAN, dgpu_temp);