net/mlx4e: Don't redefine IB_MTU_XXX enum

Rely on existing IB_MTU_XXX definitions which exist in ib_verbs.h.

Reviewed-by: Patrisious Haddad <phaddad@nvidia.com>
Signed-off-by: Mark Zhang <markzhang@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/382c91ee506e7f1f3c1801957df6b28963484b7d.1750147222.git.leon@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>