allow Thermocouple on bed only

[ellensp]

Description

User wanted just 1 Thermocouple on the bed
ie #define TEMP_SENSOR_BED -3

This results in a error

Marlin/src/module/temperature.cpp: In static member function 'static raw_adc_t Temperature::read_max_tc()':
Marlin/src/module/temperature.cpp:3531:7: error: 'TEMP_SENSOR_0_MAX_TC_TMAX' was not declared in this scope
       TEMP_SENSOR_0_MAX_TC_TMAX,

several small issue where found.

The tests to set HAS_MAX_TC, HAS_MAX6675, HAS_MAX31855 and HAS_MAX31865 where called to soon, before TEMP_SENSOR_BED_IS_MAX6675, TEMP_SENSOR_BED_IS_MAX31855 and TEMP_SENSOR_BED_IS_MAX31865 where set,
So this code was moved down a little so they get set correctly

A block of code for Thermocouple on hotends was not correctly guarded.
Used #if HAS_MAX_TC , but that includes beds with a thermocouple

updated to use #if TEMP_SENSOR_IS_MAX_TC(0) || TEMP_SENSOR_IS_MAX_TC(1) || TEMP_SENSOR_IS_MAX_TC(2)

Also removed a compiler warning due to TEMP_SENSOR_BED_MAX_TC_TMAX being presumed to be a int vs a max_tc_temp_t

Requirements

#define TEMP_SENSOR_BED -3

Benefits

Builds as expected