ixgbevf: Cleanup accounting for space needed at start of xmit_frame
ixgbevf: Cleanup accounting for space needed at start of xmit_frame

This change cleans up the accounting needed at the start of xmit_frame so
that we can avoid doing too much work to determine how many descriptors we
will need.

Signed-off-by: Alexander Duyck <af56634f9be8457194a3461ec96c497f138af4ff@intel.com>
Signed-off-by: Greg Rose <fdff95cc3a51f0ebfc2cd0523e9ef9af6ad07484@intel.com>
Tested-by: Sibai Li <7b32709b4fa5663a47e0d1f9518bcee0920157c8@intel.com>
Signed-off-by: Jeff Kirsher <87e35f5be20bb3e67f4ba6b86f5f6be3085b1b3a@intel.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas