mfd: rz-mtu3: Link time dependencies

mfd: rz-mtu3: Link time dependencies

The new set of drivers for RZ/G2L MTU3a tries to enable compile-testing the
individual client drivers even when the MFD portion is disabled but gets it
wrong, causing a link failure when the core is in a loadable module but the
other drivers are built-in:

x86_64-linux-ld: drivers/pwm/pwm-rz-mtu3.o: in function `rz_mtu3_pwm_apply':
pwm-rz-mtu3.c:(.text+0x4bf): undefined reference to `rz_mtu3_8bit_ch_write'
x86_64-linux-ld: pwm-rz-mtu3.c:(.text+0x509): undefined reference to `rz_mtu3_disable'

arm-linux-gnueabi-ld: drivers/counter/rz-mtu3-cnt.o: in function `rz_mtu3_cascade_counts_enable_get':
rz-mtu3-cnt.c:(.text+0xbec): undefined reference to `rz_mtu3_shared_reg_read'

It seems better not to add the extra complexity here but instead just use
a normal hard dependency, so remove the #else portion in the header along
with the "|| COMPILE_TEST". This could also be fixed by having slightly more
elaborate Kconfig dependencies or using the cursed 'IS_REACHABLE()' helper,
but in practice it's already possible to compile-test all these drivers
by enabling the mtd portion.

Fixes: 254d3a727421c ("pwm: Add Renesas RZ/G2L MTU3a PWM driver")
Fixes: 0be8907359df4 ("counter: Add Renesas RZ/G2L MTU3a counter driver")
Fixes: 654c293e1687b ("mfd: Add Renesas RZ/G2L MTU3a core driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230719090430.1925182-1-arnd@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>