target/arm: Fix coding style issues in gdbstub code in helper.c

target/arm: Fix coding style issues in gdbstub code in helper.c

We're going to move this code to a different file; fix the coding
style first so checkpatch doesn't complain.  This includes deleting
the spurious 'break' statements after returns in the
vfp_gdb_get_reg() function.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210921162901.17508-3-peter.maydell@linaro.org