Field regmap of struct visconti_pll_provider is never used. Remove it.
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

Link: https://lore.kernel.org/r/20230302205028.2539197-1-dario.binacchi@amarulasolutions.comAcked-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>