Remove the unnecessary CONFIG_RPMSG_UART_CONSOLE preprocessor guard around
the console registration logic in uart_rpmsg_init().
The uart_rpmsg_init() function already accepts a bool isconsole parameter to
dynamically control console registration, which is designed to support flexible
console setup in distributed multi-core SOC systems. Adding the macro check on
top of this runtime parameter is redundant and negates the dynamic registration
capability.
This change fixes a regression introduced by PR #18410, which broke the functionality
of sim/rpproxy and sim/rpserver due to the incorrect macro guard preventing proper
console registration for the rpmsg UART device.
Signed-off-by: chao an <anchao.archer@bytedance.com>