ArmVirtPkg/PlatformBootManagerLib: return to "-kernel before boot devices"

ArmVirtPkg/PlatformBootManagerLib: return to "-kernel before boot devices"

Move the TryRunningQemuKernel() call back to its original place. This
improves the UEFI boot time for VMs that have "-kernel", many disks or
NICs, and no "bootindex" properties. A well-known example is
guestfish/libguestfs.

For more info on the TryRunningQemuKernel() location, see the following
commits: 23d04b58e27b, a78c4836ea0b, 158990b941e4.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Xiang Zheng <xiang.zheng@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>