drm/msm/a4xx: add a405_registers for a405 device

A405 device has a different set of registers than a4xx_registers.  It
has no VMIDMT or XPU registers, and VBIF registers are different.  Let's
add a405_registers for a405 device.

As adreno_is_a405() works only after adreno_gpu_init() gets called, the
assignments get moved down after adreno_gpu_init().

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Jordan Crouse <jcrouse@codeauorora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>