4.1.7.1 SERCOM_IsRxReady

#define SERCOM_IsRxReady SERCOM__IsRxReady

Macro workaround for a macro issue in uart.

MISRA C:2012 Deviation Advisory: misra-c2012- 8.9  

Justification: This cannot be followed since the value of the variables must be saved until the next time the function is called. Declaring at block scope will make managing the variable reset more difficult. MISRA C:2012 Deviation Advisory: misra-c2012- 15.4  

Justification: This will not be followed because it would require removing code that is helpful for debugging, making the code more difficult to work with.