The plat_arm_mmap variable is already declared in plat_arm.h, which is
included from plat/arm/common/arm_common.c.

Similarly, plat_arm.h declares the 'plat_arm_psci_pm_ops' variable, which
does not need to be declared again in plat/arm/common/arm_pm.c.

The duplication was not compliant with MISRA rule 8.5.

Change-Id: Icc42547cc025023226b1078a7ec4f06d093364b7
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>