wil6210: pmc logger bug fix

When allocating pmc descriptor, the structure is
initially created on stack and later copied to
the physical ring (device) memory. The descriptor
structure must be initialized to zero to avoid
garbage configuration, which may result in pmc
mechanism malfunctioning.

Signed-off-by: Vladimir Shulman <QCA_shulmanv@QCA.qualcomm.com>
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>