tcg/sparc: Convert patch_reloc to return bool

tcg/sparc: Convert patch_reloc to return bool

Since 7ecd02a06f8, if patch_reloc fails we restart translation
with a smaller TB.  SPARC had its function signature changed,
but not the logic.  Replace assert with return false.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>