dri3: initialize adaptive_sync as false before configQueryb

dri3: initialize adaptive_sync as false before configQueryb

Fixes following errors from valgrind output:

   ==23388== Conditional jump or move depends on uninitialised value(s)
   ==23388==    at 0x48B4924: loader_dri3_drawable_init (loader_dri3_helper.c:381)
   ==23388==    by 0x48A97D2: dri3_create_drawable (dri3_glx.c:386)
   ==23388==    by 0x489E190: driFetchDrawable (dri_common.c:369)
   ==23388==    by 0x48A9187: dri3_bind_context (dri3_glx.c:195)
   ==23388==    by 0x488B75C: MakeContextCurrent (glxcurrent.c:220)
   ==23388==    by 0x488B8DB: glXMakeCurrent (glxcurrent.c:267)
   ==23388==    by 0x10A987: ??? (in /usr/bin/glxgears)
   ==23388==    by 0x4BEB412: (below main) (in /usr/lib64/libc-2.28.so)
   ==23388==
   ==23388== Conditional jump or move depends on uninitialised value(s)
   ==23388==    at 0x48B5A40: loader_dri3_swap_buffers_msc (loader_dri3_helper.c:923)
   ==23388==    by 0x48A9B7E: dri3_swap_buffers (dri3_glx.c:587)
   ==23388==    by 0x4887A81: glXSwapBuffers (glxcmds.c:857)
   ==23388==    by 0x10ADED: ??? (in /usr/bin/glxgears)
   ==23388==    by 0x4BEB412: (below main) (in /usr/lib64/libc-2.28.so)

Fixes: 2e12fe425fe "loader/dri3: Enable adaptive_sync via _VARIABLE_REFRESH property"
Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>