Rename macros (MAX, MIN) in src/boards/utilities.h

[adixmasz]

Each time I update loraMac-node library in my project I have problems with that macros.
That names (MAX and MIN) are extremely popular in many external libraries.

I kindly ask for rename that macros to library specific names, like:

#ifndef LMN_MIN
#define LMN_MIN( a, b ) ( ( ( a ) < ( b ) ) ? ( a ) : ( b ) )
#endif

#ifndef LMN_MAX
#define LMN_MAX( a, b ) ( ( ( a ) > ( b ) ) ? ( a ) : ( b ) )
#endif

I always change it myself just after fork and it started to be exhausting.