meta-arm/oeqa: ignore initrd warning in qemuarm64-secureboot

With kernel 6.18 the kernel will now warn if it tries to run a command
from a ramdisk but it cannot be found[1]. This happens with the
qemuarm64-secureboot machine (but not qemuarm64) because u-boot appears
to be populating the devicetree with a ramdisk entry:

    loading kernel to address 40400000 size 1702a00
      1  qfw          ready   qfw          0  qfw
    ** Booting bootflow 'qfw' with qfw
    ## Flattened Device Tree blob at 7e659890
       Booting using the fdt blob at 0x7e659890
    Working FDT set to 7e659890
       Loading Ramdisk to 7bcfd000, end 7d3ffa00 ... OK
       Loading Device Tree to 000000007d621000, end 000000007d626534 ... OK
    Working FDT set to 7d621000

    Starting kernel ...

The kernel tries to mount and boot this ramdisk but fails because it
isn't a valid initrd or initramfs. The boot continues as usual, but this
warning in the logs triggers parselogs.

Until the boot flow is properly resolved, ignore the message.

[1] linux 98aa4d5d242d ("init/main.c: add warning when file specified in rdinit is inaccessible")

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/lib/oeqa/runtime/cases/parselogs-ignores-qemuarm64-secureboot.txt

@@ -1,3 +1,8 @@
 optee: Failed to initialize async notifications: -95
 ARM FF-A: Failed to register driver sched callback -95
 ARM FF-A: Notification setup failed -95, not enabled
+
+# u-boot appears to be telling the kernel via devicetree that it has an initrd,
+# but it doesnt. The blob appears to be the same size as the kernel, which is
+# interesting. Until this is resolved, ignore the warning.
+check access for rdinit=/init failed: -2, ignoring