serial: Fix SIFIVE debug serial dependency

The commit 4cc24aea ("serial: Add missing Kconfig dependencies for
debug consoles") has added incorrect dependency for SIFIVE debug uart which
should depend on SIFIVE driver instead of PL01x.

Fixes: 4cc24aea ("serial: Add missing Kconfig dependencies for debug consoles")
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NBin Meng <bin.meng@windriver.com>
Reviewed-by: NLeo Liang <ycliang@andestech.com>
Reviewed-by: NSean Anderson <seanga2@gmail.com>

drivers/serial/Kconfig

@@ -359,7 +359,7 @@ config DEBUG_UART_SANDBOX
 
 config DEBUG_UART_SIFIVE
 	bool "SiFive UART"
-	depends on PL01X_SERIAL
+	depends on SIFIVE_SERIAL
 	help
 	  Select this to enable a debug UART using the serial_sifive driver. You
 	  will need to provide parameters to make this work. The driver will