package/mesa3d: add missing elfutils dependency with R600 and RadeonSI driver

package/mesa3d: add missing elfutils dependency with R600 and RadeonSI driver

Commit "add dependency on elfutils for R600 with LLVM" [1] select
elfutils package at Kconfig level without adding it the make dependency.

Enabling r600 support lead to a build issue when building from
scratch with "make mesa3d".

Fixes:
checking for RADEON... yes
configure: error: r600 requires libelf when using llvm

elfutils dependency is needed by r600 with llvm support and radeonSI.

Fixes:
checking for RADEON... yes
checking for AMDGPU... yes
configure: error: radeonsi requires libelf when using llvm

Add a new BR2_PACKAGE_MESA3D_NEEDS_ELFUTILS hidden Config.in boolean
selected by R600 and RadeonSI at Kconfig level.
When selected, BR2_PACKAGE_MESA3D_NEEDS_ELFUTILS add elfutils dependency
at make level.

[1] 92fda8761aa8024be53a8edb8c102d1ba6401bce

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Michał Kalbarczyk <michal@gamecodehq.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>