ice: code cleanup in ice_sched.c

This patch does some clean up in the Tx scheduler code:

1. Adjust the stack variable usage
2. Modify the debug prints to display the FW error
3. Add additional debug prints while adding/removing VSIs

Signed-off-by: Victor Raj <victor.raj@intel.com>
Reviewed-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>