msm: kgsl: Dont crash the device if the zap shader is not found

If there are problems loading the zap shader or if the zap ucode
is not found in the build system, do not crash the device.
Instead, just propagate the error up the stack.

Change-Id: I2f9d821dbe3dbfb8708cb41e630876cce7571696
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>