crashkernel: optimize arm64 reserved size if PAGE_SIZE=4k

The arm64 platform supports either 64KB or 4KB page size. In the case of 4KB page size, the reserved memory size can be aligned to that on x86_64.

Introducing a new formula for 4KB on arm64, which bases on x86_64 plus extra 64MB.

Signed-off-by: Pingfan Liu piliu@redhat.com