net/mlx5: HWS, Init mutex on the correct path

The newly introduced mutex is only used for reformat actions, but it was
initialized for modify header instead.

The struct that contains the mutex is zero-initialized and an all-zero
mutex is valid, so the issue only shows up with CONFIG_DEBUG_MUTEXES.

Fixes: b206d9ec ("net/mlx5: HWS, register reformat actions with fw")
Signed-off-by: Vlad Dogaru <vdogaru@nvidia.com>
Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Signed-off-by: Mark Bloch <mbloch@nvidia.com>
Link: https://patch.msgid.link/20250610151514.1094735-5-mbloch@nvidia.com


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