clk: keystone: syscon-clk: Add support for AM62 epwm-tbclk

AM62 has 3 instances of EPWM modules. Each EPWM module has
an EPWM TBCLKEN module input used to individually enable or
disable its EPWM time-base clock. The EPWM time-base clock
enable input comes from the CTRLMMR_EPWM_TB_CLKEN register
bits 0 to 2 in CTRL_MMR0 module (6.1.1.4.1.48 [1]). This
is virtually the same setup as in AM64 but with 3 instead
of 9 clock providers on AM62.

Update the driver with the 3 instances of clocks associated
to a new compatible: "ti,am62-epwm-tbclk".

[1] https://www.ti.com/lit/pdf/spruiv7



Signed-off-by: Georgi Vlaev <g-vlaev@ti.com>
Tested-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20220415190343.6284-3-g-vlaev@ti.com


Reviewed-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>