entry_offset wrong/deprected for recent linux kernels

[userid0x0]

Hi,
I noticed the entry_offset in https://github.com/seL4/camkes-vm/blob/master/templates/seL4VMParameters.template.c#L23 is set to a deprecated value of 0x80000 for ARMv8/9. Within the Linux 5.8-5.10 timeframe the mandatory offset of 0x80000 was removed, compare [1]. This causes recent kernels to emit a error message [Firmware Bug]: Kernel image misaligned at boot, please fix your bootloader!.

The real fix would be to detect the AARCH64 image header [2] and to automatically apply the text_offset which is 0x80000 for old kernels and 0x0 for recent kernels.

[1] https://www.spinics.net/lists/arm-kernel/msg798878.html
[2] https://www.kernel.org/doc/Documentation/arm64/booting.txt