package/libunwind: simplify architecture dependencies

package/libunwind: simplify architecture dependencies

BR2_ARM_CPU_HAS_ARM already embeddeds the fact that this is an ARM chip,
so (BR2_arm || BR2_armeb) is forcibly true when BR2_ARM_CPU_HAS_ARM is.

In other words, BR2_ARM_CPU_HAS_ARM can't be true unless either BR2_arm
or BR2_armeb itslef is true.

Simplify the logic accordingly.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Romain Naour <romain.naour@openwide.fr>
Acked-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>