Skip ramdisk check for some devices in FirmwareBootHeaderVerification

This ramdisk check is handled by vts_generic_boot_image_test for
devices with kernels greater than version 5.10.
The rest of the test case can stay since it is checking the recovery image.

Test: atest FirmwareBootHeaderVerification # on device with 5.10 kernel
Bug: 231639760
Change-Id: I8e13b62268d950df701e6d4ab27b0f1ab2245a98
Merged-In: I8e13b62268d950df701e6d4ab27b0f1ab2245a98