libdl: fix size parameter when unmap library in dlclose
libdl: fix size parameter when unmap library in dlclose

Fix size parameter when unmap a library by means of dlclose, by
taking into account the p_vaddr of first PT_LOAD segment, so it works
also for prelinked shared objects.
Unmapping of dlopen shared libraries is broken since
94cc6edb78a12655c0602a246fa1cbdc8c6d0ad9

Signed-off-by: Filippo Arcidiacono <26825f07340f791bc0d38da89fcffcd93550a83c@st.com>
Signed-off-by: Carmelo Amoroso <532378793705a04edd56deb76ad8c0442834d55d@st.com>

foss-xtensa/uClibc,hwoarang/uClibc,atgreen/uClibc-moxie,atgreen/uClibc-moxie,majek/uclibc-vx32,ddcc/klee-uclibc-0.9.33.2,majek/uclibc-vx32,mephi42/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,ffainelli/uClibc,ddcc/klee-uclibc-0.9.33.2,ndmsystems/uClibc,brgl/uclibc-ng,brgl/uclibc-ng,foss-xtensa/uClibc,ffainelli/uClibc,ndmsystems/uClibc,waweber/uclibc-clang,skristiansson/uClibc-or1k,skristiansson/uClibc-or1k,majek/uclibc-vx32,kraj/uclibc-ng,czankel/xtensa-uclibc,wbx-github/uclibc-ng,waweber/uclibc-clang,hwoarang/uClibc,mephi42/uClibc,brgl/uclibc-ng,hwoarang/uClibc,ddcc/klee-uclibc-0.9.33.2,groundwater/uClibc,majek/uclibc-vx32,hjl-tools/uClibc,mephi42/uClibc,groundwater/uClibc,kraj/uClibc,wbx-github/uclibc-ng,waweber/uclibc-clang,kraj/uclibc-ng,ffainelli/uClibc,hjl-tools/uClibc,ffainelli/uClibc,groundwater/uClibc,waweber/uclibc-clang,foss-for-synopsys-dwc-arc-processors/uClibc,wbx-github/uclibc-ng,ndmsystems/uClibc,foss-xtensa/uClibc,skristiansson/uClibc-or1k,foss-xtensa/uClibc,czankel/xtensa-uclibc,atgreen/uClibc-moxie,ddcc/klee-uclibc-0.9.33.2,atgreen/uClibc-moxie,hjl-tools/uClibc,hjl-tools/uClibc,mephi42/uClibc,hwoarang/uClibc,hjl-tools/uClibc,czankel/xtensa-uclibc,ffainelli/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,ndmsystems/uClibc,czankel/xtensa-uclibc,wbx-github/uclibc-ng,kraj/uclibc-ng,skristiansson/uClibc-or1k,groundwater/uClibc,kraj/uClibc,brgl/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,kraj/uClibc,kraj/uclibc-ng,kraj/uClibc,groundwater/uClibc