ASoC: audio-ext-clk: fix number of clocks for lnbb clk

ln_bb_clk2 is defined in a different array than the rest of the
clocks. Use the right array to calculate the number of clocks in
that array to avoid possible over allocation of memory.

Change-Id: I7e68e15d037810840605a7d86dd54eaf6c6cc427
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>