Change TPS546 undervoltage and shutdown voltage thresholds to better values.

[aaron3481]

Change the UV_WARN limit cuz 5.8V is not make sense for Ultra and Supra and Gamma which input voltage is 5V

[skot]

for some reason my TPS546 doesn't like this setting!

I (903) TPS546.c: Setting VIN_OFF: 4.00
I (913) TPS546.c: Setting VIN_UV_WARN_LIMIT: 4.20
E (913) i2c.master: I2C transaction unexpected nack detected
E (923) i2c.master: s_i2c_synchronous_transaction(872): I2C transaction failed
E (933) i2c.master: i2c_master_transmit(1074): I2C transaction failed

[skot]

for some reason I get the I2C NACK whenever TPS546_INIT_VIN_UV_WARN_LIMIT is set below 5.0V