package/boost: atomics needs always lockfree atomic bytes

package/boost: atomics needs always lockfree atomic bytes

Since version 1.74.0, boost atomics needs a toolchain that always
supports lockfree atomic bytes so add dependendy on
BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS:
https://github.com/boostorg/atomic/issues/42

Fixes:
 - http://autobuild.buildroot.org/results/c03a786791e3aa7801cf1bff9934c4a105f54ce1

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[yann.morin.1998@free.fr:
  - add the new dependency as its own 'depends on' line
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>