subsys/tracing: add names to Kconfig choice symbols

This commit adds names to Kconfig choice sysmbols. This allows for their
selection from Kconfig, e.g.:

    choice TRACING_FORMAT_CHOICE
    	default TRACING_TEST if CONFIG_FOO
	default TRACING_CTF if CONFIG_BAR
    endchoice

Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>