hwrng: atmel - move set of TRNG_HALFR in atmel_trng_init()

Move set of TRNG_HALFR in atmel_trng_init() as this function is
also called on resume path. In case of SAMA7G5 where backup and
self-refresh PM mode is available most of the SoC parts are
powered of (including TRNG) when entering suspend. In that case
on resuming path TRNG_HALFR should also be re-configured.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>