drm/i915/psr: Allow writing PSR2_MAN_TRK_CTL using DSB

Allow writing PSR2_MAN_TRK_CTL using DSB by using intel_de_write_dsb. Do
not check intel_dp->psr.lock being held when using DSB. This assertion
doesn't make sense as in case of using DSB the actual write happens later
and we are not taking intel_dp->psr.lock mutex over dsb commit.

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250213064804.2077127-7-jouni.hogander@intel.com