msm: kgsl: Fix uninitialized variables

NULL initialize cfg and seq variables. Uninitialized values of these
variables could result in not returning from a6xx_load_pdc_ucode function
when we fail to map either PDC CFG or PDC SEQ memory regions.

Fixes: 8b370ecd ("msm: kgsl: Do not program GPU PDC ucode and TCS commands")
Change-Id: Ie5d00da8261546e58ae07b2fc5ba1d7d483fb53f
Signed-off-by: Raghu Ananya Arabolu <rarabolu@codeaurora.org>