Don't use QT_ARCH to detect ARM or OpenGL ES 2 on ARM

Don't use QT_ARCH to detect ARM or OpenGL ES 2 on ARM

Use Q_PROCESSOR_ARM instead of QT_ARCH_ARM.

On maemo6, don't use QT_ARCH==armv6 to conditionally include egl
code. Instead check for opengles2 in QT_CONFIG, which is detected
by the configure script.

Change-Id: Ib3062fbd81c3a3acd318df32c49ad133a5b0d07c
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>