msm: vidc: change error msg for max sessions condition

When the max sessions condition is reached, the firmware
sends session init to the driver. Change the error message
from 'core is in a bad state' to reflect the actual
behavior.

CRs-fixed: 625684
Change-Id: Iddf7d3fc72c1c2696200789954c1e69fd0419dca
Signed-off-by: Pushkaraj Patil <ppatil@codeaurora.org>