gallium/targets: Make use of prebuilt libdricommon.la.

gallium/targets: Make use of prebuilt libdricommon.la.

libdricommon.la is available whenever a non swrast driver is built.
All the classic dri drivers make use of the prebuild library but all
of the gallium ones rebuild it explicitly.

While we're here gallium/{llvm,soft}pipe does not require HAVE_COMMON_DRI
thus do not set in during configure.

v2: [Emil] Add commit message and drop HAVE_COMMON_DRI from configure.ac
v3: [Emil] Rebase and resolve targets/r*/dri conflicts

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>