When system uses fw direct loading, then psp context structure won't be
initiliazed. And it is also unable to execute mode reset.

[  434.601474] amdgpu 0000:0c:00.0: GPU reset begin!
[  434.694326] amdgpu 0000:0c:00.0: GPU reset
[  434.743152] BUG: unable to handle kernel NULL pointer dereference at
0000000000000058
[  434.838474] IP: psp_gpu_reset+0xc/0x30 [amdgpu]
[  434.893532] PGD 406ed9067
[  434.893533] P4D 406ed9067
[  434.926376] PUD 400b46067
[  434.959217] PMD 0
[  435.033379] Oops: 0000 [#1] SMP
[  435.072573] Modules linked in: amdgpu(OE) chash(OE) gpu_sched(OE) ttm(OE)
drm_kms_helper(OE) drm(OE) fb_sys_fops syscopyarea sysfillrect sysimgblt
rpcsec_gss_krb5 auth_rpcgss nfsv4 nfs lockd grace fscache snd_hda_codec_realtek
snd_hda_codec_generic snd_hda_codec_hdmi snd_hda_intel snd_hda_codec
snd_hda_core snd_hwdep snd_pcm edac_mce_amd snd_seq_midi snd_seq_midi_event
kvm_amd snd_rawmidi kvm irqbypass crct10dif_pclmul crc32_pclmul snd_seq
ghash_clmulni_intel snd_seq_device pcbc snd_timer eeepc_wmi aesni_intel snd
asus_wmi aes_x86_64 sparse_keymap crypto_simd glue_helper joydev soundcore
wmi_bmof cryptd video i2c_piix4 shpchp 8250_dw i2c_designware_platform mac_hid
i2c_designware_core sunrpc parport_pc ppdev lp parport autofs4 hid_generic igb
usbhid dca ptp mxm_wmi pps_core ahci hid i2c_algo_bit
[  435.931754]  libahci wmi

Signed-off-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>