System76 common board directory (#53)

* Move configuration for battery into board.mk

* lemp9: remove tcpm code

* Move touchpad to its own module

* Add kbled_reset to all platforms, move items to run on CPU reset to a function

* Add defines for battery and charger address

* Add I2C_0 export to it5570e

* Move common system76 board functions into src/board/system76/common

src/board/system76/common/pwm.c

@@ -0,0 +1,24 @@
+#include <board/pwm.h>
+
+void pwm_init(void) {
+    // Set T0CHSEL to TACH0A and T1CHSEL to TACH1A
+    TSWCTLR = 0;
+
+    // Disable PWM
+    ZTIER = 0;
+
+    // Set prescalar clock frequency to EC clock
+    PCFSR = 0b01;
+
+    // Set clock prescaler to 0 + 1
+    C0CPRS = 0;
+
+    // Set cycle time to 255 + 1
+    CTR0 = 255;
+
+    // Turn off CPU fan (temperature control in peci_event)
+    DCR2 = 0;
+
+    // Enable PWM
+    ZTIER = (1 << 1);
+}