powerpc/512x: Make mpc512x_select_reset_compat() static

mpc512x_select_reset_compat() is only used in the file it
is defined.

Make it static.

Move mpc512x_restart_init() after mpc512x_select_reset_compat().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/36a19e13025dbf17e92e832dd24150642b0e9bad.1692341499.git.christophe.leroy@csgroup.eu