rpi-userland: add bcm_host to egl.pc

bcm_host is the Broadcom hardware interface library
And is currently a dependency to use the EGL functions

Signed-off-by: Floris Bos <bos@je-eigen-domein.nl>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>