Try increasing the delay inside this function.
void lcd_data(char data1)
{
P0=data1;
RS=1;
RW=0;
E=1;
delay(10);
E=0;
}
Have you tried any simple program to display a character or a sting in the LCD?
One more thing is that directly writing the serial data received to an LCD is not a good method, since the LCD writing may consume significant time and there is a chance chance of missing the serial data.