clk: analogbits: add Wide-Range PLL library

Add common library code for the Analog Bits Wide-Range PLL (WRPLL) IP
block, as implemented in TSMC CLN28HPC.

There is no bus interface or register target associated with this PLL.
This library is intended to be used by drivers for IP blocks that
expose registers connected to the PLL configuration and status
signals.

Based on code originally written by Wesley Terpstra
<wesley@sifive.com>:
https://github.com/riscv/riscv-linux/commit/999529edf517ed75b56659d456d221b2ee56bb60

This version incorporates several changes requested by Stephen
Boyd <sboyd@kernel.org>.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Wesley Terpstra <wesley@sifive.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Megan Wachs <megan@sifive.com>
Cc: linux-clk@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
[sboyd@kernel.org: Fix some const issues]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>