dsound: Constify some variables

[Andrew Talbot]

Changelog:
    dsound: Constify some variables.

diff --git a/dlls/dsound/propset.c b/dlls/dsound/propset.c
index 0645610..04c7b58 100644
--- a/dlls/dsound/propset.c
+++ b/dlls/dsound/propset.c
@@ -344,7 +344,7 @@ static HRESULT DSPROPERTY_EnumerateW(
     return S_OK;
 }
 
-static BOOL DSPROPERTY_descWtoA(DSPROPERTY_DIRECTSOUNDDEVICE_DESCRIPTION_W_DATA *dataW,
+static BOOL DSPROPERTY_descWtoA(const DSPROPERTY_DIRECTSOUNDDEVICE_DESCRIPTION_W_DATA *dataW,
                                 DSPROPERTY_DIRECTSOUNDDEVICE_DESCRIPTION_A_DATA *dataA)
 {
     DWORD modlen, desclen;
@@ -372,7 +372,7 @@ static BOOL DSPROPERTY_descWtoA(DSPROPERTY_DIRECTSOUNDDEVICE_DESCRIPTION_W_DATA
     return TRUE;
 }
 
-static void DSPROPERTY_descWto1(DSPROPERTY_DIRECTSOUNDDEVICE_DESCRIPTION_W_DATA *dataW,
+static void DSPROPERTY_descWto1(const DSPROPERTY_DIRECTSOUNDDEVICE_DESCRIPTION_W_DATA *dataW,
                                 DSPROPERTY_DIRECTSOUNDDEVICE_DESCRIPTION_1_DATA *data1)
 {
     data1->DeviceId = dataW->DeviceId;