gallium/radeon: Add libamd_common.a to TARGET_LIB_DEPS also for r600

gallium/radeon: Add libamd_common.a to TARGET_LIB_DEPS also for r600

Fixes build failure with --enable-opencl --enable-xvmc:

make[4]: Entering directory '/home/daenzer/src/mesa-git/mesa/build-amd64/src/gallium/targets/xvmc'
  CXXLD    libXvMCgallium.la
../../../../src/gallium/drivers/r600/.libs/libr600.a(evergreen_compute.o): In function `evergreen_create_compute_state':
/home/daenzer/src/mesa-git/mesa/build-amd64/src/gallium/drivers/r600/../../../../../src/gallium/drivers/r600/evergreen_compute.c:254: undefined reference to `ac_elf_read'
../../../../src/gallium/drivers/r600/.libs/libr600.a(evergreen_compute.o): In function `r600_shader_binary_read_config':
/home/daenzer/src/mesa-git/mesa/build-amd64/src/gallium/drivers/r600/../../../../../src/gallium/drivers/r600/evergreen_compute.c:189: undefined reference to `ac_shader_binary_config_start'
/home/daenzer/src/mesa-git/mesa/build-amd64/src/gallium/drivers/r600/../../../../../src/gallium/drivers/r600/evergreen_compute.c:189: undefined reference to `ac_shader_binary_config_start'
collect2: error: ld returned 1 exit status
Makefile:760: recipe for target 'libXvMCgallium.la' failed

Fixes: dc4c551a345d ("radeon/ac: switch from radeon_elf_read() to ac_elf_read()")
Acked-by: Timothy Arceri <tarceri@itsqueeze.com>
Tested-by: Timothy Arceri <tarceri@itsqueeze.com>