arch: riscv: irq: fix build warning
arch: riscv: irq: fix build warning

In arch_irq_connect_dynamic the 'level' variable is only used on
platforms that define CONFIG_RISCV_HAS_PLIC.  For the other platforms
we'll get a warning about an unused variable.  Remove the need for
'level' and just call irq_get_level() where its needed to address the
issue.

Signed-off-by: Kumar Gala <a5e5248af4cd4f0ed8c515f61d40a6e2db46a66e@linaro.org>

zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr