firmware: arm_scpi: Check the DVFS OPP count returned by the firmware

In the Linux kernel, the following vulnerability has been resolved:

firmware: arm_scpi: Check the DVFS OPP count returned by the firmware

Fix a kernel crash with the below call trace when the SCPI firmware

returns OPP count of zero.

dvfs_info.opp_count may be zero on some platforms during the reboot

test, and the kernel will crash after dereferencing the pointer to

kcalloc(info->count, sizeof(*opp), GFP_KERNEL).

| Unable to handle kernel NULL pointer dereference at virtual address 0000000000000028

| Mem abort info:

| ESR = 0x96000004

| Exception class = DABT (current EL), IL = 32 bits

| SET = 0, FnV = 0

| EA = 0, S1PTW = 0

| Data abort info:

| ISV = 0, ISS = 0x00000004

| CM = 0, WnR = 0

| user pgtable: 4k pages, 48-bit VAs, pgdp = 00000000faefa08c

| [0000000000000028] pgd=0000000000000000

| Internal error: Oops: 96000004 [#1] SMP

| scpi-hwmon: probe of PHYT000D:00 failed with error -110

| Process systemd-udevd (pid: 1701, stack limit = 0x00000000aaede86c)

| CPU: 2 PID: 1701 Comm: systemd-udevd Not tainted 4.19.90+ #1

| Hardware name: PHYTIUM LTD Phytium FT2000/4/Phytium FT2000/4, BIOS

| pstate: 60000005 (nZCv daif -PAN -UAO)

| pc : scpi_dvfs_recalc_rate+0x40/0x58 [clk_scpi]

| lr : clk_register+0x438/0x720

| Call trace:

| scpi_dvfs_recalc_rate+0x40/0x58 [clk_scpi]

| devm_clk_hw_register+0x50/0xa0

| scpi_clk_ops_init.isra.2+0xa0/0x138 [clk_scpi]

| scpi_clocks_probe+0x528/0x70c [clk_scpi]

| platform_drv_probe+0x58/0xa8

| really_probe+0x260/0x3d0

| driver_probe_device+0x12c/0x148

| device_driver_attach+0x74/0x98

| __driver_attach+0xb4/0xe8

| bus_for_each_dev+0x88/0xe0

| driver_attach+0x30/0x40

| bus_add_driver+0x178/0x2b0

| driver_register+0x64/0x118

| __platform_driver_register+0x54/0x60

| scpi_clocks_driver_init+0x24/0x1000 [clk_scpi]

| do_one_initcall+0x54/0x220

| do_init_module+0x54/0x1c8

| load_module+0x14a4/0x1668

| __se_sys_finit_module+0xf8/0x110

| __arm64_sys_finit_module+0x24/0x30

| el0_svc_common+0x78/0x170

| el0_svc_handler+0x38/0x78

| el0_svc+0x8/0x340

| Code: 937d7c00 a94153f3 a8c27bfd f9400421 (b8606820)

| ---[ end trace 06feb22469d89fa8 ]---

| Kernel panic - not syncing: Fatal exception

| SMP: stopping secondary CPUs

| Kernel Offset: disabled

| CPU features: 0x10,a0002008

| Memory Limit: none