MdeModulePkg/RegularExpressionDxe: Fix memory assert in FreePool()

MdeModulePkg/RegularExpressionDxe: Fix memory assert in FreePool()

Memory buffer that is allocated by malloc() and realloc() will be
shifted by 8 bytes because Oniguruma keeps its memory signature. This 8
bytes shift is not handled while calling free() to release memory. Add
free() function to check Oniguruma signature before release memory
because memory buffer is not touched when using calloc().

Signed-off-by: Nickle Wang <nickle.wang@hpe.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>