gdb/arm: Include FType bit in EXC_RETURN pattern on v8m

For v8m, the EXC_RETURN pattern, without security extension, consists of
FType, Mode and SPSEL.  These are the same bits that are used in v7m.
This patch extends the list of patterns to include also the FType bit
and not just Mode and SPSEL bits for v8m targets without security
extension.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>