[Buildroot] [Bug 6854] Update to Qt 5.2.1

[Peter Kuemmel]

> Von: "Vicente Olivert Riera" <Vincent.Riera at imgtec.com>
> 
> I was testing Qt-5.2.1. I agree with the removal of these patches:
> 
> qt5base-0001-Fix-build-MIPS64-bigendian.patch
> qt5base-0007-detect-posix_fallocate-at-configure-time.patch

These patches were merged into Qt 5.2.1.

> 
> -- 
> Vincent
>