fm10k: remove unnecessary variable initializer

The err variable in the fm10k_tlv_attr_parse function is initialized
with zero. However, the function never reads err without first assigning
it from a function call. Remove this unnecessary initialization.

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

[fm10k_tlv.c:498]: (style) Variable 'err' is assigned a value that is
never used.

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>