dt-bindings: mfd: stericsson,db8500-prcmu: Spelling s/Cortex A-/Cortex-A/

Fix a misspelling of "Cortex-A9".

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/0789000f012122a7fa27ef709c738101b00cd834.1693407196.git.geert+renesas@glider.be


Signed-off-by: Lee Jones <lee@kernel.org>