qemu: rename virFirmware*Free() functions to have more accurate names

qemu: rename virFirmware*Free() functions to have more accurate names

Several functions had the names virFirmware[something]Free(), but they
aren't taking a pointer to some object and freeing it. Instead, they
are making a copy of the content of an entire object, then Freeing the
objects pointed to by that content.

As a first step in a too-complicated cleanup just to eliminate a few
occurrences of VIR_FREE(), this patch renames those functions to more
accurately reflect what they do - they Free the *Content* of their
arguments.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>