stress-ng: link libatomic instead of disabling atomics

stress-ng: link libatomic instead of disabling atomics

Drop 002-disable-atomics-mips-and-ppc.patch. It papered over link errors for
64-bit atomics on MIPS and PPC, which happen because stress-ng strips -latomic
whenever $(CC) matches "musl-gcc" -- as our cross toolchains do. Pass
LIB_ATOMIC=-latomic instead; libatomic is already in DEPENDS. Its stress-fractal
hunk was in any case dead since upstream 24c30b7fa narrowed the row counter back
to int32_t, which MIPS32 and PPC32 increment atomically inline.

Signed-off-by: Alexandru Ardelean <redacted>