powerpc/32: Dismantle EXC_XFER_STD/LITE/TEMPLATE

In order to get more control in exception prolog, dismantle
all non standard exception macros, finishing with EXC_XFER_STD
and EXC_XFER_LITE and EXC_XFER_TEMPLATE.

Also remove transfer_to_handler_full and ret_from_except and
ret_from_except_full as they are not used anymore.

Last parameter of EXCEPTION() is now ignored, will be removed
in a later patch to avoid too much churn.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/ca5795d04a220586b7037dbbbe6951dfa9e768eb.1615552867.git.christophe.leroy@csgroup.eu