mesa: use #if over #ifdef in the FEATURE_ES1 check to fix a build failure.
mesa: use #if over #ifdef in the FEATURE_ES1 check to fix a build failure.

mfeatures.h will define FEATURE_ES1 to 0 if it's not defined yet.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=53664

Signed-off-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>

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