riscv32: linker: Link .srodata section
riscv32: linker: Link .srodata section

Building tests/kernel/common/kernel.common with the new crosstools
SDK-ng resulted in an orphan short read-only data section. Fix this by
adding the .srodata section to the RISC-V linker script.

Signed-off-by: Nathaniel Graff <e7e2d91f1deb937cded6d6fc8e8292f24ce08299@sifive.com>

ldts/zephyr,ldts/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,Vudentz/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,ldts/zephyr,explora26/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,explora26/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,galak/zephyr,explora26/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr