[PATCH] powerpc: Don't use toc in decrementer_iSeries_masked

Since 404849bb we've been using
LOAD_REG_ADDRBASE, which uses the toc pointer, in decrementer_iSeries_masked.

This can explode if we take the decrementer interrupt while we're in a module,
because the toc pointer in r2 will be the module's toc pointer.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>