ARM: at91: sfr: convert to Kconfig

This converts the at91 sfr to Kconfig

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
diff --git a/arch/arm/mach-at91/Makefile b/arch/arm/mach-at91/Makefile
index 045ac88..cbd0ed6 100644
--- a/arch/arm/mach-at91/Makefile
+++ b/arch/arm/mach-at91/Makefile
@@ -7,10 +7,11 @@
 obj-$(CONFIG_AT91SAM9M10G45) += mpddrc.o spl_at91.o
 obj-$(CONFIG_AT91SAM9N12) += mpddrc.o spl_at91.o
 obj-$(CONFIG_AT91SAM9X5) += mpddrc.o spl_at91.o
-obj-$(CONFIG_SAMA5D2) += bootparams_atmel.o mpddrc.o spl_atmel.o matrix.o atmel_sfr.o
+obj-$(CONFIG_SAMA5D2) += bootparams_atmel.o mpddrc.o spl_atmel.o matrix.o
 obj-$(CONFIG_SAMA5D3) += bootparams_atmel.o mpddrc.o spl_atmel.o
-obj-$(CONFIG_SAMA5D4) += bootparams_atmel.o mpddrc.o spl_atmel.o matrix.o atmel_sfr.o
+obj-$(CONFIG_SAMA5D4) += bootparams_atmel.o mpddrc.o spl_atmel.o matrix.o
 obj-y += spl.o
+obj-$(CONFIG_ATMEL_SFR) += atmel_sfr.o
 endif
 
 obj-y += clock.o