stm class: Kconfig: correct symbol name

stm class: Kconfig: correct symbol name

Drop the leading "CONFIG_" when referring to Kconfig symbols--
it is supplied by the kconfig software.
This make the default values work as (apparently) expected.

Fixes: a02509f301c6 ("stm class: Factor out default framing protocol")
Fixes: d69d5e83110f ("stm class: Add MIPI SyS-T protocol support")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20251228190502.2480758-1-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>