Revert "[RISCV] Disable linker relaxation for now"

This reverts commit 7a59be26.

The new clang update (r547379) does not have the linker relaxation bug
anymore so we can revert this workaround.

Bug: 390197215
Test: m net_test_stack and mmma packages/modules/Bluetooth
Change-Id: I10260faaf2d249afffe0ff406bc27c2931817794