powerpc/cell: Fix clang -Wimplicit-fallthrough warning

Clang warns:

arch/powerpc/platforms/cell/pervasive.c:81:2: error: unannotated fall-through between switch labels
        case SRR1_WAKEEE:
        ^
arch/powerpc/platforms/cell/pervasive.c:81:2: note: insert 'break;' to avoid fall-through
        case SRR1_WAKEEE:
        ^
        break;
1 error generated.

Clang is more pedantic than GCC, which does not warn when failing
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. Add athe missing
break to silence the warning.

Fixes: 6e83985 ("powerpc/cbe: Do not process external or decremeter interrupts from sreset")
Reported-by: Naresh Kamboju <[email protected]>
Signed-off-by: Anders Roxell <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Reviewed-by: Arnd Bergmann <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

arch/powerpc/platforms/cell/pervasive.c

@@ -78,6 +78,7 @@ static int cbe_system_reset_exception(struct pt_regs *regs)
 	switch (regs->msr & SRR1_WAKEMASK) {
 	case SRR1_WAKEDEC:
 		set_dec(1);
+		break;
 	case SRR1_WAKEEE:
 		/*
 		 * Handle these when interrupts get re-enabled and we take