package/mplayer: disable inline asm on i386

package/mplayer: disable inline asm on i386

A similar fix was committed to ffmpeg in the past:
https://git.buildroot.net/buildroot/commit/package/ffmpeg?id=bfb8df2ad9b164b421d25294c6882c8b61dc59a5
which will be reverted with another patch.

Mplayer contains ffmpeg 3.0, with current ffmpeg 3.2.4 the bug is gone,
the difference between both revisions is too big in order to find a
real fix for the problem.

Special cflags, added by
https://git.buildroot.net/buildroot/commit/package/multimedia/mplayer?id=fd38100e1189d19cad87a64c52df2c773eb47e40
are no longer needed now so remove them as well.

Testing these defconfigs did not produce compile errors with current
ffmpeg but with mplayer:

BR2_i386=y
BR2_x86_i586=y
BR2_GCC_VERSION_4_8_X=y

BR2_i386=y
BR2_x86_i586=y
BR2_GCC_VERSION_5_X=y

BR2_i386=y
BR2_x86_i586=y
BR2_GCC_VERSION_6_X=y

BR2_i386=y
BR2_x86_i486=y
BR2_GCC_VERSION_5_X=y

BR2_i386=y
BR2_x86_i686=y
BR2_GCC_VERSION_5_X=y

BR2_i386=y
BR2_x86_pentium_mmx=y
BR2_GCC_VERSION_5_X=y

BR2_i386=y
BR2_x86_corei7=y
BR2_GCC_VERSION_5_X=y

Fixes
http://autobuild.buildroot.net/results/030/03066dd8937ef4c75d62f237fd195df92b247ee2//
and many others.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>