Fix benchmark projects makefiles to use proper configuration for i8253

Fix benchmark projects makefiles to use i8253 specific configuration
for only two variants of generic_pc BSP - pentium4 and minuteia, but
not for the whole BSP.

Change-Id: Iac89e29d2e26ee411d9c2d2fbcd3335c0e71fb06
Signed-off-by: Dmitriy Korovkin <dmitriy.korovkin@windriver.com>
3 files changed