sysutils/edk2@bhyve: Fix main firmware

EDK2 produce multiple files for the bhyve flavor, _CODE and _DATA
The PLAT_RESULT is just a concat of both.
But bhyve doesn't support having only one file.
When it was its own port we just install the _CODE file as the main file
instead of using the concat one generated during edk2 build.
For this port we need to use the main PLAT_RESULT files for all flavors
except bhyve so add a quirks in the install phase that just replace the main
file with the _CODE one.
Thanks to Corvin Köhne <CorvinK@beckhoff.com> for helping me understanding
the issue.

Fixes: 2e6a6ccd15 ("sysutils/edk2: Add bhyve as a new FLAVOR of edk2")
Sponsored by: Beckhoff Automation GmbH & Co. KG
PR: 264338