mux: adg792a: remove incorrect of_match_ptr annotation

mux: adg792a: remove incorrect of_match_ptr annotation

Building with W=1 shows a warning about adg792a_of_match being unused
when CONFIG_OF is disabled:

drivers/mux/adg792a.c:134:34: error: unused variable 'adg792a_of_match' [-Werror,-Wunused-const-variable]

Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250409122314.2848028-4-arnd@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>