drm/xe/relay: Don't use GFP_KERNEL for new transactions

VFs use a relay transaction during the resume/reset flow and use
of the GFP_KERNEL flag may conflict with the reclaim:

     -> #0 (fs_reclaim){+.+.}-{0:0}:
 [ ]        __lock_acquire+0x1874/0x2bc0
 [ ]        lock_acquire+0xd2/0x310
 [ ]        fs_reclaim_acquire+0xc5/0x100
 [ ]        mempool_alloc_noprof+0x5c/0x1b0
 [ ]        __relay_get_transaction+0xdc/0xa10 [xe]
 [ ]        relay_send_to+0x251/0xe50 [xe]
 [ ]        xe_guc_relay_send_to_pf+0x79/0x3a0 [xe]
 [ ]        xe_gt_sriov_vf_connect+0x90/0x4d0 [xe]
 [ ]        xe_uc_init_hw+0x157/0x3b0 [xe]
 [ ]        do_gt_restart+0x1ae/0x650 [xe]
 [ ]        xe_gt_resume+0xb6/0x120 [xe]
 [ ]        xe_pm_runtime_resume+0x15b/0x370 [xe]
 [ ]        xe_pci_runtime_resume+0x73/0x90 [xe]
 [ ]        pci_pm_runtime_resume+0xa0/0x100
 [ ]        __rpm_callback+0x4d/0x170
 [ ]        rpm_callback+0x64/0x70
 [ ]        rpm_resume+0x594/0x790
 [ ]        __pm_runtime_resume+0x4e/0x90
 [ ]        xe_pm_runtime_get_ioctl+0x9c/0x160 [xe]

Since we have a preallocated pool of relay transactions, which
should cover all our normal relay use cases, we may use the
GFP_NOWAIT flag when allocating new outgoing transactions.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Tested-by: Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>
Reviewed-by: Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250131153713.808-1-michal.wajdeczko@intel.com