v1.2.0.1.1

k32w1: fix TLS handshaking

Double the OPENTHREAD_CONFIG_HEAP_INTERNAL_SIZE (to 16k)
so that TLS handshaking succeeds.

A smaller size will cause the process to fail with
memory allocation error (MBEDTLS_ERR_MPI_ALLOC_FAILED -0x0010)

Signed-off-by: George Stefan <[email protected]>