Revert "leds-pca955x: Remove the unused function pca95xx_num_led_regs()"

This reverts commit 38bcb51f.

This function is needed by the hardware blink support just introduced.
Also rename the function to pca955x_num_led_regs() to match the rest of
the functions in the driver.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20250221155144.2109806-1-eajames@linux.ibm.com


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