clk: at91: port Linux v5.6 SAM9X60 (new ARM926EJ-S) clock support ...

During a bug hunt that ultimately turned out unrelated to the state
of the barebox at91 clk driver, I synchronized its state with Linux v5.6.

Bug fixes and clean up to minimize the diff were split out in separate
prior commits.  This last commit imports the rest, which is basically
support for Microchip's new ARM926EJ-S SoC, the SAM9x60.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

clk: at91: delete no-longer required DT compat code ...

Unlike Linux, we don't require barebox drivers to support old device
tree bindings. Following device tree compatibles are no longer present
in barebox latest import of dts/:

 * atmel,sama5d2-clk-generated
 * atmel,sama5d4-clk-h32mx
 * atmel,at91sam9g45-clk-pll
 * atmel,at91sam9g20-clk-pllb
 * atmel,at91sam9260-clk-slow

Drop their compat code.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

clk: at91: delete dead i2s/audio code ...

They aren't used anywhere, thus drop them.

Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

clk: at91: add dt-compat to PMC bindings ...

As the sama5d3 based microchip-ksz9477-evb board still uses the old
bindings, the dt-compat.c code is ported as well. This can be removed
when all in-kernel at91 boards have been ported to the new bindings.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Ladislav Michl <ladis@linux-mips.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>