xilinx: versal: Enable i2c mux uclass with pca954x driver

Xilinx is using pca954x i2c muxes on a lot of boards that's why enable this
driver by default.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/c090aea3436c7a4ebe698da6cbc70e70a14baae3.1659691195.git.michal.simek@amd.com