Bluetooth: Use higher RX_BUF_LEN when Mesh Proxy protocol is used
Bluetooth: Use higher RX_BUF_LEN when Mesh Proxy protocol is used

Avoiding segmentation in the GATT-based Mesh Proxy protocol requires
having an RX buffer length of at least 77. We could round it up to 80
since there's otherwise wasted space, however there's also
BT_HCI_RESERVE to consider, so to avoid pushing over the 4-byte
boundary for certain HCI drivers just leave the size at 77.

Signed-off-by: Johan Hedberg <628991c7b0a19c384f9b99c21ec330ce952bb838@intel.com>

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