BaseTools/DevicePath: fix GCC build error in print_mem(), and clean it up

Currently "BaseTools/Source/C/DevicePath/DevicePath.c" fails to build with
GCC48:

> DevicePath.c: In function 'print_mem':
> DevicePath.c:109:5: error: 'for' loop initial declarations are only
> allowed in C99 mode
>      for (size_t i=0; i<n; i++) {
>      ^
> DevicePath.c:109:5: note: use option -std=c99 or -std=gnu99 to compile
> your code

In addition, the print_mem() function does not conform to the edk2 coding
style:

- we use CamelCase and no underscores in identifiers,
- the types and type qualifiers should follow the edk2 style,
- initialization as part of definition is forbidden for local variables.

Clean these up.

While updating the print_mem()/PrintMem() call sites, also remove the
superfluous parentheses around the second argument.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Fixes: 7dbc50bd244d95fdc1741b9cfc561f0bfd724de1
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>