ixgbevf: fix proper type for error code in ixgbevf_resume()

The variable 'err' in ixgbevf_resume() is used to store the return value
of different functions, which return an int. Currently, 'err' is
declared as u32, which is semantically incorrect and misleading.

In the Linux kernel, u32 is typically reserved for fixed-width data
used in hardware interfaces or protocol structures. Using it for a
generic error code may confuse reviewers or developers into thinking
the value is hardware-related or size-constrained.

Replace u32 with int to reflect the actual usage and improve code
clarity and semantic correctness.

No functional change.

Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Jedrzej Jagielski <jedrzej.jagielski@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>