Commit eba1b6b3c724 ("plat/poplar: migrate to mmc framework") defines
variable 'info' without !POPLAR_RECOVERY protection, and hence causes
the following unused variable error with POPLAR_RECOVERY=1 build.

plat/hisilicon/poplar/bl1_plat_setup.c: In function ‘bl1_platform_setup’:
plat/hisilicon/poplar/bl1_plat_setup.c:95:25: error: unused variable ‘info’ [-Werror=unused-variable]
  struct mmc_device_info info;
                         ^~~~

The patches fixes the build error with POPLAR_RECOVERY=1.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>