Add the 32-bit vdso Makefile to the vdso_install rule so that 'make
vdso_install' installs the 32-bit compat vdso when it is compiled.

Fixes: a7f71a2c ("arm64: compat: Add vDSO")
Signed-off-by: NStephen Boyd <swboyd@chromium.org>
Reviewed-by: NVincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: NWill Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20200818014950.42492-1-swboyd@chromium.orgSigned-off-by: NCatalin Marinas <catalin.marinas@arm.com>