ShellPkg/AcpiView: Fix field validator invocation

ShellPkg/AcpiView: Fix field validator invocation

Bugzilla: 3046 (https://bugzilla.tianocore.org/show_bug.cgi?id=3046)

The field validator function provides means to validate fields
in the ACPI table structures. To print complex field types a
print formatter function is provided.

The field validator was being invoked for simple data fields
for which the default print format is used. However, the field
validator function was not invoked if a print formatter function
was provided.

This problem is noticed when a Generic Address Structure (GAS)
is printed using DumpGas() and a field validator is present
to validate the GAS structure.

To fix this move the invocation of the field validator after
the field is printed such that the validation function is
called even when a print formatter function is present.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>