drivers: thermal: cpu-cooling: Fix random cpu frequency min request

cpu cooling assumes last frequency level in frequency table is zero
and it initializes that value as default floor frequency request.
But max frequency level index is used for core isolation and it is
not initialized with any value. It leads to a case where random
value is set as default floor request.

Initialize cpu frequency max level frequency as zero to avoid above
scenario.

Change-Id: Ie3c98f0a29bd38c49b5196d41156102c9095bad7
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>