powerpc/powernv: Fix section mismatch from opal_lpc_init()

opal_lpc_init() is called from an __init routine, and calls other __init
routines, so should also be __init, init?

Fixes: 023b13a5 ("powerpc/powernv: Add support for direct mapped LPC on POWER9")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>