egl: remove custom bcm21553 tls code

The original code seems to work just as well.

Change-Id: Iaf96cade40d909316763b1be839c6f54ca147856
opengl: allow direct TLS access for ARMv6-VFP arch

When ARCH_ARM_HAVE_TLS_REGISTER is true, build opengl libraries
in arm mode (to workaround the missing MCR/MRC registers in thumb
mode).

Change-Id: I319e40d333c5b6808ce098164e27df9064bff706