samus_pd: remove dead code around allowing PD negotiation

Remove code for preventing PD negotiation until the battery
is at some minimum SOC. This was originally necessary because
transitioning voltages would cause the source voltage to go
briefly to 0V, which would kill power to the system unless
the battery was at some minimum level of charge. But, that
isn't true anymore. It is safe to transition up or down in
voltage and the source voltage should never drop to 0V.

BUG=chrome-os-partner:29499
BRANCH=none
TEST=make -j buildall. No need to do any more testing because
this code has been disabled for a while.

Change-Id: I8a3dca117f01f0f9c7d04b5d489e4a8588a89be6
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/211021
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

include/config.h

@@ -908,10 +908,6 @@
 /* USB PD MCU slave address for host commands */
 #define CONFIG_USB_PD_I2C_SLAVE_ADDR 0x3c
 
-/* TODO(crosbug.com/p/29499): Determine threshold for power negotiation */
-/* USB PD minimum battery charge to negotiate for more power */
-#define CONFIG_USB_PD_MIN_BATT_CHARGE 1
-
 /* Compile chip support for the USB device controller */
 #undef CONFIG_USB
 

include/usb_pd.h

@@ -208,13 +208,6 @@ void pd_request_source_voltage(int port, int mv);
  */
 int pd_board_checks(void);
 
-/**
- * Query if power negotiation is allowed.
- *
- * @return true if negotation is allowed, false otherwise.
- */
-int pd_power_negotiation_allowed(void);
-
 /*
  * Handle Vendor Defined Message with our vendor ID.
  *