samples: intel_s1000: remove DCACHE_WRITEBACK

Remove DCACHE_WRITEBACK Kconfig variable from DMIC sample app project
Cache configuration is fixed and the cache operation routines
internally take appropriate action based on the cache configuration.

Signed-off-by: Sathish Kuttan <sathish.k.kuttan@intel.com>
diff --git a/samples/boards/intel_s1000_crb/dmic/prj.conf b/samples/boards/intel_s1000_crb/dmic/prj.conf
index a5bd6a5..594e4a3 100644
--- a/samples/boards/intel_s1000_crb/dmic/prj.conf
+++ b/samples/boards/intel_s1000_crb/dmic/prj.conf
@@ -1,7 +1,6 @@
 CONFIG_LOG=y
 
 CONFIG_DMA=y
-CONFIG_DCACHE_WRITEBACK=y
 
 CONFIG_USB=n
 CONFIG_I2C=y