fm10k: reduce the scope of qv local variable

Reduce the scope of the qv vector pointer local variable in the
fm10k_set_coalesce function.

This was detected by cppcheck and resolves the following style warning
produced by that tool:

[fm10k_ethtool.c:658]: (style) The scope of the variable 'qv' can be
reduced.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>