bsc: gsm0808: Fix return code in bsc_compl_l3

complete_layer3 returns true if everything succeeded, false otherwise.
However, its caller bsc_compl_l3 returns unix style (0 sucess,
negative error).

This commit has no real effect since only caller of bsc_compl_l3 never
checks return code, but will check it in the future.

Change-Id: I722696c3f6402288b51d6fcf51f478b3b0c9f0f0
1 file changed