ufs: renesas: Update Kconfig entry help text

ufs: renesas: Update Kconfig entry help text

The current Renesas UFS driver contains initialization code
that is specific to R-Car S4 R8A779F0. The upcoming R-Car X5H
initialization code is different and contained in a separate
driver. Update the Kconfig entry help text for the current
driver to help discern it from the X5H driver. No functional
change.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Link: https://patch.msgid.link/20251028142335.18125-6-marek.vasut+renesas@mailbox.org
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>