driver: clock-control: imx-ccm-rev2: get_rate(FLEXSPI2) returns FLEXSPI1 clock rate

[Finomnis]

Describe the bug
When querying the Clock Rate through clock_control_get_rate(ccm, IMX_CCM_FLEXSPI2_CLK, &rate), the returned rate is of FLEXSPI1, not FLEXSPI2.

This is due to an incorrect case statement in the driver code of imx-ccm-rev2.

This bug was found on an MIMXRT1176 based work project.

To Reproduce
I tried to reproduce it on an MIMXRT1176-EVKB board, but didn't get it to boot. It booted fine with the 'hello_world' example, but enabling CONFIG_FLASH made it not output anything any more on UART. I was unable to reproduce it therefore with a publically available board, although it should be trivial once someone understands how to enable FLEXSPI (to be precise, CONFIG_MEMC_MCUX_FLEXSPI) while still getting the board to boot.

That said, the error is simple to reproduce through code review and already fixed on main soon:
#79217

However, it needs backporting to v3.7, as it's still broken on the v3.7-branch, which is the current LTS.