clk: rockchip: Fix PLL bandwidth

In the TRM we see that BWADJ is "a 12-bit bus that selects the values
1-4096 for the bandwidth divider (NB)":
 NB = BWADJ[11:0] + 1
The recommended setting of NB: NB = NF / 2.

So:
  NB = NF / 2
  BWADJ[11:0] + 1 = NF / 2
  BWADJ[11:0] = NF / 2 - 1

Right now, we have:

{                                               \
        .rate   = _rate##U,                     \
        .nr = _nr,                              \
        .nf = _nf,                              \
        .no = _no,                              \
        .bwadj = (_nf >> 1),                    \
}

That means we set bwadj to NF / 2, not NF / 2 - 1

All of this is a bit confusing because we specify "NR" (the 1-based
value), "NF" (the 1-based value), "NO" (the 1-based value), but
"BWADJ" (the 0-based value) instead of "NB" (the 1-based value).

Let's change to working with "NB" and fix the off by one error.  This
may affect PLL jitter in a small way (hopefully for the better).

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>