RISC-V: stop directly selecting drivers for SOC_CANAAN

The serial and clock drivers will be enabled by default if the symbol
itself is enabled, so stop directly selecting the drivers in
Kconfigs.socs.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

arch/riscv/Kconfig.socs

@@ -56,12 +56,9 @@ config SOC_CANAAN
 	bool "Canaan Kendryte K210 SoC"
 	depends on !MMU
 	select CLINT_TIMER if RISCV_M_MODE
-	select SERIAL_SIFIVE if TTY
-	select SERIAL_SIFIVE_CONSOLE if TTY
 	select ARCH_HAS_RESET_CONTROLLER
 	select PINCTRL
 	select COMMON_CLK
-	select COMMON_CLK_K210
 	help
 	  This enables support for Canaan Kendryte K210 SoC platform hardware.