common/cnxk: update CPU directive in NPA assembly code
common/cnxk: update CPU directive in NPA assembly code

Use arch_extension instead of .cpu directive in NPA assembly code
snippets. Using .cpu directive with generic causes it to override
the micro architecture selected by march,mcpu.
For example if march=armv8.5-a+crypto+sve2 provided then the .cpu
directive overrides it to generic+crypto+sve2, use arch_extension
to get the expected result.

Signed-off-by: Ashwin Sekhar T K <b45fa93d246de8ace97bf9e06c737641b7430ac2@marvell.com>
Acked-by: Jerin Jacob <352c4d4f9291b869992ddb67daa45ddc149fed30@marvell.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk