Remove redundant sse2 math flags

Qtbase already enables sse2 math by default now. This version is no
longer needed and may actually hurt performance by triggering scheduling
for pentium4.

Change-Id: Ib3b6781fb0b92c1351344cc2d2f13101fa2b632b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>