lame: Disable debug symbols for Aarch64 and MIPS

Building lame with debug symbols needs the following macros to be
defined: _FPU_MASK_IM, _FPU_MASK_ZM, _FPU_MASK_OM.
So, if BR2_ENABLE_DEBUG is selected, then we have to force lame to be
built without debug symbols for Aarch64 and MIPS because these
architectures don't have those macros defined.

Fixes:
	http://autobuild.buildroot.net/results/721/721dff299b204b1d3ccc0846009eb17faa2d29eb/



Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>