Having compression extension in the initramfs name will make it complex
to add suport for multiple compression algorithms. So remove the
compression extension from initramfs names.

BUG=b:233589303
TEST=None

Disallow-Recycled-Builds: all
Change-Id: Idcbed273746dbe58caea5c346c8cd564013861f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/initramfs/+/3719082


Commit-Queue: Vineeth Pillai <vineethrp@google.com>
Tested-by: Vineeth Pillai <vineethrp@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Dmitry Torokhov <dtor@chromium.org>