clk: Si5341/Si5340: remove redundant assignment to n_den

clk: Si5341/Si5340: remove redundant assignment to n_den

The variable n_den is initialized however that value is never read
as n_den is re-assigned a little later in the two paths of a
following if-statement.  Remove the redundant assignment.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lkml.kernel.org/r/20190701165020.19840-1-colin.king@canonical.com
Acked-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>