mfd: wcd934x: Add page 0x50 registers for wcd934x codec

Registers for page 0x50 in the wcd934x audio codec are currently
not defined. These registers control WCD DSP register configuration
and setup. Add these register definitions so that codec driver can
read/write these registers.

CRs-Fixed: 1049012
Change-Id: If1162c09de8d4d7c330a97a1f133f6d46ce2fd74
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>