package/strace: xtensa needs headers >= 5.0

package/strace: xtensa needs headers >= 5.0

xtensa support needs user_pt_regs since version 5.6 and
https://github.com/strace/strace/commit/2429c69961e2598902bded9c02dd601b362b66b4

However user_pt_regs is only available since kernel 5.0 and
https://github.com/torvalds/linux/commit/06fbac8e8971f2fa526e189304dd95ee62f39dbe

Fixes:
 - http://autobuild.buildroot.org/results/c6c4fb3b9098c5fc5dbe4415e2a9757fc775b746

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>