bsdinstall: use consistent EFI configuration across platforms

MFC r320007:

• increase arm64 EFI partition to 200M, as x86
• use EFI_BOOTPART_SIZE and EFI_BOOTPART_PATH macros on x86
• increase ZFS EFI partition to 200M

MFC r320008: bsdinstall: correct comment after r320007

PR: 201898
Approved by: re (kib)
Relnotes: Yes
Sponsored by: The FreeBSD Foundation