php-amqp: needs openssl support in rabbitmq-c

Since version 1.8.0, php-amqp needs a rabbitmq-c with openssl support:
https://github.com/pdezwart/php-amqp/issues/310

SSL support is disabled in rabbitmq-c if BR2_STATIC_LIBS is set however
don't add an unneeded !BR2_STATIC_LIBS dependency in Config.in as all
PHP External Extensions depends on !BR2_STATIC_LIBS
(see package/Config.in)

Fixes:
 - http://autobuild.buildroot.net/results/b7c89bbbd0ca1df08dd7cbfc90c7b45dcf1fad05



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>