ASoC: ops: improve snd_soc_get_volsw

* clamp the values if the register value read is
  out of range

Signed-off-by: Niranjan H Y <niranjan.hy@ti.com>
[This patch originally had two changes in it, I removed a second buggy
 one -- broonie]
--
v5:
 - remove clamp parameter
 - move the boundary check after sign-bit extension
Link: https://patch.msgid.link/20250912083624.804-1-niranjan.hy@ti.com


Signed-off-by: Mark Brown <broonie@kernel.org>