pflash: Clean up after commit 368a354f02b, part 2

pflash: Clean up after commit 368a354f02b, part 2

Our pflash devices are simplistically modelled has having
"num-blocks" sectors of equal size "sector-length".  Real hardware
commonly has sectors of different sizes.  How our "sector-length"
property is related to the physical device's multiple sector sizes
is unclear.

Helper functions pflash_cfi01_register() and pflash_cfi02_register()
create a pflash device, set properties including "sector-length" and
"num-blocks", and realize.  They take parameters @size, @sector_len
and @nb_blocs.

QOMification left parameter @size unused.  Obviously, @size should
match @sector_len and @nb_blocs, i.e. size == sector_len * nb_blocs.
All callers satisfy this.

Remove @nb_blocs and compute it from @size and @sector_len.

Signed-off-by: Markus Armbruster <[email protected]>
Reviewed-by: Laszlo Ersek <[email protected]>
Reviewed-by: Alex Bennée <[email protected]>
Message-Id: <20190308094610[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>