powerpc: Don't hide eh field of lwarx behind a macro

The eh field must remain 0 for PPC32 and is only used
by PPC64.

Don't hide that behind a macro, just leave the responsibility
to the user.

At the time being, the only users of PPC_RAW_L{WDQ}ARX are
setting the eh field to 0, so the special handling of __PPC_EH
is useless. Just take the value given by the caller.

Same for DEFINE_TESTOP(), don't do special handling in that
macro, ensure the caller hands over the proper eh value.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
[mpe: Use 'n' constraint per Segher]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/8b9c8a1a14f9143552a85fcbf96698224a8c2469.1659430931.git.christophe.leroy@csgroup.eu