firmware: arm_scmi: use ioread64() instead of ioread64_hi_lo()

firmware: arm_scmi: use ioread64() instead of ioread64_hi_lo()

The scmi_common_fastchannel_db_ring() function calls either ioread64()
or ioread64_hi_lo() depending on whether it is compiler for 32-bit
or 64-bit architectures.

The same logic is used to define ioread64() itself in the
linux/io-64-nonatomic-hi-lo.h header file, so the special case
is not really needed.

The behavior here should not change at all.

Fixes: 6f9ea4dabd2d ("firmware: arm_scmi: Generalize the fast channel support")
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20250304144346.1025658-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>