Bug#907837: installation-guide: Please give more hints for net booting from UEFI.

[Steven De Herdt <steven.deherdt@gmail.com>]

Package: installation-guide
Severity: normal

Dear Maintainer,

Section 4.5 describes how to boot the installer via PXE.  However, with
these instructions I was not able to start d-i in UEFI mode, and
the computer didn't show a useful error message.  Searching the internet
inspired me to try debian-installer/amd64/bootnetx64.efi as the filename
to boot (instead of pxelinux.0), and that worked.  So, please add this
information to paragraph 4.5.4.

Thanks for maintaining!
-Steven