sgi/install_sgi_prerequisites: add 'autopoint' to prerequisite package list

'autopoint' package is required for build of grub. So add it to the list of
prerequisite packages to be installed.

Change-Id: I30bf3f900d1d01ed1d2faa13795cd5060b1ece0b
Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>