of: base: Fix phandle argument length mismatch error message

The cell_count field of of_phandle_iterator is the number of cells we
expect in the phandle arguments list when cells_name is missing. The
error message should show the number of cells we actually see.

Fixes: af3be70a

 ("of: Improve of_phandle_iterator_next() error message")
Cc: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/96519ac55be90a63fa44afe01480c30d08535465.1640881913.git.baruch@tkos.co.il