extmod/modbluetooth: Add API for L2CAP channels.

Also known as L2CAP "connection oriented channels". This provides a
socket-like data transfer mechanism for BLE.

Currently only implemented for NimBLE on STM32 / Unix.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

py/misc.h

@@ -53,6 +53,9 @@ typedef unsigned int uint;
 // Static assertion macro
 #define MP_STATIC_ASSERT(cond) ((void)sizeof(char[1 - 2 * !(cond)]))
 
+// Round-up integer division
+#define MP_CEIL_DIVIDE(a, b) (((a) + (b) - 1) / (b))
+
 /** memory allocation ******************************************/
 
 // TODO make a lazy m_renew that can increase by a smaller amount than requested (but by at least 1 more element)