doc: board: ti: Use prompt prompt_style to simplify documentation

The sphinx-prompt documentation[0] provides examples on how we can use
prompt as a parameter to simplify the description. Use the same.

While at it, ensure to make all relevant prompts clarified such as gdb
prompts.

[0] http://sbrunner.github.io/sphinx-prompt/



Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>