wifi: mt76: mt7921: fix error code of return in mt7921_acpi_read

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

wifi: mt76: mt7921: fix error code of return in mt7921_acpi_read

Kernel NULL pointer dereference when ACPI SAR table isn't implemented well.

Fix the error code of return to mark the ACPI SAR table as invalid.

[ 5.077128] mt7921e 0000:06:00.0: sar cnt = 0

[ 5.077381] BUG: kernel NULL pointer dereference, address:

0000000000000004

[ 5.077630] #PF: supervisor read access in kernel mode

[ 5.077883] #PF: error_code(0x0000) - not-present page

[ 5.078138] PGD 0 P4D 0

[ 5.078398] Oops: 0000 [#1] PREEMPT SMP NOPTI

[ 5.079202] RIP: 0010:mt7921_init_acpi_sar+0x106/0x220

[mt7921_common]

...

[ 5.080786] Call Trace:

[ 5.080786] <TASK>

[ 5.080786] mt7921_register_device+0x37d/0x490 [mt7921_common]

[ 5.080786] mt7921_pci_probe.part.0+0x2ee/0x310 [mt7921e]

[ 5.080786] mt7921_pci_probe+0x52/0x70 [mt7921e]

[ 5.080786] local_pci_probe+0x47/0x90

[ 5.080786] pci_call_probe+0x55/0x190

[ 5.080786] pci_device_probe+0x84/0x120