soundwire: intel: remove unused variables

Variables 'nval' and 'i' are no longer used sdw_master_read_intel_prop()
so remove them.

drivers/soundwire/intel.c: In function 'sdw_master_read_intel_prop':
drivers/soundwire/intel.c:829:12: warning: unused variable 'i' [-Wunused-variable]
  int nval, i;
            ^
drivers/soundwire/intel.c:829:6: warning: unused variable 'nval' [-Wunused-variable]
  int nval, i;
      ^~~~

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: 085f4ace ("soundwire: intel: read mclk_freq property from firmware")
Signed-off-by: Vinod Koul <vkoul@kernel.org>