soc: nrf53: fix building anomaly 168 workaround

[lopsided98]

With GCC 12.3 and binutils 2.40, the build fails with:

<...>/zephyr/arch/arm/core/cortex_m/cpu_idle.S: Assembler messages:
<...>/zephyr/arch/arm/core/cortex_m/cpu_idle.S:51: Error: junk at end of line, first unrecognized character is `n'
<...>/zephyr/arch/arm/core/cortex_m/cpu_idle.S:133:   Info: macro invoked from here

Because the SOC_ON_EXIT_CPU_IDLE macro puts all the statements on a single line, there must be a semicolon after .rept. Presumably it works without the semicolons on some compiler, but I'm not sure which one.

[github-actions]

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[carlescufi]

Compliance are false positives.

[github-actions]

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