target/riscv: remove break after g_assert_not_reached()

target/riscv: remove break after g_assert_not_reached()

This patch is part of a series that moves towards a consistent use of
g_assert_not_reached() rather than an ad hoc mix of different
assertion mechanisms.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-ID: <20240919044641.386068-23-pierrick.bouvier@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>