sysutils/ec2-scripts: Update to 1.11

While I'm here:

• Fetch distfile directly from github,
• Remove the NOFIRSTBOOT option, which was only useful on FreeBSD

releases prior to FreeBSD 11.0, all of which have long since ceased
to be supported.

• Add a dependency on sysutils/ebsnvme-id, which is used by the new

version of these scripts.