Usually, C has no problem up-converting types to larger bit sizes. MISRA
rule 10.7 requires that you not do this, or be very explicit about this.
This resolves the following required rule:

    bl1/aarch64/bl1_context_mgmt.c:81:[MISRA C-2012 Rule 10.7 (required)]<None>
    The width of the composite expression "0U | ((mode & 3U) << 2U) | 1U |
    0x3c0U" (32 bits) is less that the right hand operand
    "18446744073709547519ULL" (64 bits).

This also resolves MISRA defects such as:

    bl2/aarch64/bl2arch_setup.c:18:[MISRA C-2012 Rule 12.2 (required)]
    In the expression "3U << 20", shifting more than 7 bits, the number
    of bits in the essential type of the left expression, "3U", is
    not allowed.

Further, MISRA requires that all shifts don't overflow. The definition of
PAGE_SIZE was (1U << 12), and 1U is 8 bits. This caused about 50 issues.
This fixes the violation by changing the definition to 1UL << 12. Since
this uses 32bits, it should not cr...