riscv: Do not build reset.c if SYSRESET is on

SYSRESET uclass driver already provides all the reset APIs, hence
exclude our own ad-hoc reset.c implementation.
Signed-off-by: NBin Meng <bin.meng@windriver.com>
Reviewed-by: NSagar Kadam <sagar.kadam@sifive.com>
Reviewed-by: NPragnesh Patel <pragnesh.patel@sifive.com>

arch/riscv/lib/Makefile

@@ -20,7 +20,9 @@ obj-$(CONFIG_SBI) += sbi.o
 obj-$(CONFIG_SBI_IPI) += sbi_ipi.o
 endif
 obj-y	+= interrupts.o
+ifeq ($(CONFIG_$(SPL_)SYSRESET),)
 obj-y	+= reset.o
+endif
 obj-y   += setjmp.o
 obj-$(CONFIG_$(SPL_)SMP) += smp.o
 obj-$(CONFIG_SPL_BUILD)	+= spl.o