Design: tail is not needed
Present function set has no benefit from the tail member. It is removable.
Bug: Wrong allocation size
Code allocates enough for a pointer rather than enough for the struct.
Cast not needed. Better to allocate to the de-referenced object than type.
// node temp=(node)malloc(sizeof(node));
node temp = malloc(sizeof *node);
Function declarations say nothing about signature
void foo(); allows later calls like foo(1), foo("hello", 5.0) to pass undetected as errors.
// void delete_front();
// void count();
// void display();
// void delete_last();
void delete_front(void);
void count(void);
void display(void);
void delete_last(void);
Inconsistent spacing
Use an auto-formatter - life is too short for manual formatting.
Lack of error checking
No checking if scanf("%d",&choice); succeeded, nor malloc().
Unneeded code
temp=NULL; serves nor purpose in node_add(int x)
Bug: de-referencing of NULL
delete_front() does not check if head == NULL before head->link. tail is not updated to NULL when last link deleted.
Bug: de-referencing of NULL
delete_last() does not check if p->link == NULL before p->link->link. Also expect head to be updated to NULL if last node deleted.