missing system calls in Counter driver APIs

[andrewboie]

We do not have system calls implemented for some of the counter APIs, preventing access from user mode.

counter_is_counting_up()
counter_get_num_of_channels()
counter_get_frequency()
counter_us_to_ticks()
counter_ticks_to_us()
counter_get_max_top_value()
counter_cancel_channel_alarm()

[andrewboie]

Most of these pull values out of dev->config->config_info

config_info is a struct in ROM and should be directly readable by user mode.
We might be able to implement a generic k_driver_config_get() system call which returns a pointer to the config struct, and these APIs could be done in terms of that, rather than a syscall for each one.