package/hiredis: fix install step for static build only

package/hiredis: fix install step for static build only

The previous patch [1] didn't take into acount the static build only
scenario. It tries to unconditionally install a shared library.

Handle the install step like for bzip2 package: install the shared
library only if BR2_SHARED_LIBS or BR2_SHARED_STATIC_LIBS is set and
install the static library only if BR2_STATIC_LIBS or
BR2_SHARED_STATIC_LIBS is set.

[1] 96daacb720cffe1f83259462bef9d3da92925cd9

Fixes:
http://autobuild.buildroot.net/results/6be/6be8024dd664af83fcf49ede29c8ad59a37f73d1

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>