package/gensio: fix detection of openssl with -latomic

package/gensio: fix detection of openssl with -latomic

Add an upstream patch to fix --with-openssl argument and allow gensio to use
pkg-config to retrieve openssl dependencies otherwise the detection of
openssl will fail on architecture that needs to link with -latomic such as
sparc v8 32 bits:

configure:9379: checking for openssl/ssl.h in /home/fabrice/buildroot/output/host/sparc-buildroot-linux-uclibc/sysroot/usr
configure:9386: result: yes
configure:9402: checking whether compiling and linking against OpenSSL works
Trying link with OPENSSL_LDFLAGS=-L/home/fabrice/buildroot/output/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib; OPENSSL_LIBS=-lssl -lcrypto; OPENSSL_INCLUDES=-I/home/fabrice/buildroot/output/host/sparc-buildroot-linux-uclibc/sysroot/usr/include
configure:9424: /home/fabrice/buildroot/output/host/bin/sparc-linux-gcc -o conftest -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -Os   -static -I/home/fabrice/buildroot/output/host/sparc-buildroot-linux-uclibc/sysroot/usr/include -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -static -L/home/fabrice/buildroot/output/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib conftest.c -lssl -lcrypto  -lpthread >&5
/home/fabrice/buildroot/output/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/8.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: /home/fabrice/buildroot/output/host/sparc-buildroot-linux-uclibc/sysroot/usr/lib/libssl.a(ssl_lib.o): in function `CRYPTO_UP_REF.isra.6':
ssl_lib.c:(.text+0x3c8): undefined reference to `__atomic_fetch_add_4'

Fixes:
 - No autobuilder failures (silent error)

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>