riscv: remove cache enablement in start.S

Cache could be enabled in harts_early_init board-specific hook,
so remove cache enablement in start.S

Signed-off-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S
index a9e1935..8e58f64 100644
--- a/arch/riscv/cpu/start.S
+++ b/arch/riscv/cpu/start.S
@@ -210,10 +210,6 @@
 	bnez	s2, secondary_hart_loop
 #endif
 
-	/* Enable cache */
-	jal	icache_enable
-	jal	dcache_enable
-
 #ifdef CONFIG_DEBUG_UART
 	jal	debug_uart_init
 #endif