i2c: rcar: Fix Wvoid-pointer-to-enum-cast warning

i2c: rcar: Fix Wvoid-pointer-to-enum-cast warning

'i2c_types' is an enum, thus cast of pointer on 64-bit compile test with
clang and W=1 causes:

  i2c-rcar.c:1144:18: error: cast to smaller integer type 'enum rcar_i2c_type' from 'const void *' [-Werror,-Wvoid-pointer-to-enum-cast]

One of the discussions in 2023 on LKML suggested warning is not suitable
for kernel.  Nothing changed in this regard since that time, so assume
the warning will stay and we want to have warnings-free builds.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20251126182257.157439-6-krzysztof.kozlowski@oss.qualcomm.com