Free all the DMC payloads, not just DMC_MAIN.

unreferenced object 0xffff88ff32d4d800 (size 1024):
  comm "kworker/1:5", pid 701, jiffies 4294904239 (age 109.736s)
  hex dump (first 32 bytes):
    40 40 00 0c 03 00 00 00 00 00 00 00 00 00 00 00  @@..............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000ba9d0d95>] dmc_load_work_fn+0x34d/0x510 [i915]
    [<000000001049fcab>] process_one_work+0x261/0x550
    [<00000000eeb995ac>] worker_thread+0x49/0x3c0
    [<0000000021031dc3>] kthread+0x10b/0x140
    [<000000004a0f69ee>] ret_from_fork+0x1f/0x30
unreferenced object 0xffff88ff0bde4000 (size 1024):
  comm "kworker/0:3", pid 708, jiffies 4294904469 (age 108.816s)
  hex dump (first 32 bytes):
    40 40 00 0c 01 00 00 00 00 00 00 00 00 00 00 00  @@..............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000ba9d0d95>] dmc_load_work_fn+0x34d/0x510 [i915]
    [<000000001049fcab>] process_one_work+0x261/0x550
    [<00000000eeb995ac>] worker_thread+0x49/0x3c0
    [<0000000021031dc3>] kthread+0x10b/0x140
    [<000000004a0f69ee>] ret_from_fork+0x1f/0x30

Fixes: 3d5928a1 ("drm/i915/xelpd: Pipe A DMC plugging")
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210809194805.3793060-1-lucas.demarchi@intel.com
(cherry picked from commit 064b877d)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>