soc: riscv: esp32c3: add z_bss_zero in startup code

replaces the plain memcpy to zero the bss with
the standard zephyr function that does this task.

Signed-off-by: Felipe Neves <ryukokki.felipe@gmail.com>
Signed-off-by: Felipe Neves <felipe.neves@espressif.com>
2 files changed