mfd: mt6397: Do not use generic name for keypad sub-devices

mfd: mt6397: Do not use generic name for keypad sub-devices

Do not use "mtk-pmic-keys" when creating sub-device for the keypad to
make sure the keypad driver will only bind to the sub-device if it has
support for the variant/has matching compatible.

Cc: stable@vger.kernel.org
Fixes: 6e31bb8d3a63 ("mfd: mt6397: Add initial support for MT6328")
Fixes: de58cee8c6b8 ("mfd: mt6397-core: Add MT6357 PMIC support")
Fixes: 4a901e305011 ("mfd: mt6397-core: Add resources for PMIC keys for MT6359")
Reported-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Tested-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com> # on
Link: https://lore.kernel.org/r/r4k3pgd3ew3ypne7ernxuzwgniiyvzosbce4cfajbcu7equblt@yato35tjb3lw
Signed-off-by: Lee Jones <lee@kernel.org>