i3c: master: svc: Fix implicit fallthrough in svc_i3c_master_ibi_work()

i3c: master: svc: Fix implicit fallthrough in svc_i3c_master_ibi_work()

Clang warns (or errors with CONFIG_WERROR=y):

  drivers/i3c/master/svc-i3c-master.c:596:2: error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough]
    596 |         default:
        |         ^
  drivers/i3c/master/svc-i3c-master.c:596:2: note: insert 'break;' to avoid fall-through
    596 |         default:
        |         ^
        |         break;
  1 error generated.

Clang is a little more pedantic than GCC, which does not warn when
falling through to a case that is just break or return. Clang's version
is more in line with the kernel's own stance in deprecated.rst, which
states that all switch/case blocks must end in either break,
fallthrough, continue, goto, or return. Add the missing break to silence
the warning.

Fixes: 0430bf9bc1ac ("i3c: master: svc: Fix missing STOP for master request")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250319-i3c-fix-clang-fallthrough-v1-1-d8e02be1ef5c@kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>