py/mpconfig.h: Define BITS_PER_BYTE only if not already defined.
It's a common macro that is possibly defined in headers of systems/SDKs
MicroPython is embedded into.
@@ -1610,7 +1610,9 @@ typedef double mp_float_t;
#define BYTES_PER_WORD (sizeof(mp_uint_t))
#endif
+#ifndef BITS_PER_BYTE
#define BITS_PER_BYTE (8)
+#endif
#define BITS_PER_WORD (BITS_PER_BYTE * BYTES_PER_WORD)
// mp_int_t value with most significant bit set
#define WORD_MSBIT_HIGH (((mp_uint_t)1) << (BYTES_PER_WORD * 8 - 1))
