mfd: syscon: atmel-smc: Remove unused helpers/macros

All macros prefixed with AT91[SAM9]_SMC have been replaced by equivalent
definitions prefixed with ATMEL_SMC, and the at91sam9_smc_xxxx() helpers
are no longer used.
Drop these definitions before someone starts using them again.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>