patch.bbclass: Ensure the DATE and SRCDATE variable exclusions apply to the correct function
People have noticed that sstate is now getting invalidated very readily. The
issue is that the code using these variables was factored into a new function
but the variable exclusion was not. This patch moves the variable exclusion
to the correct place allowing the sstate checksums to work correctly.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
