[ARM] pxafb: fix the warning of incorrect lccr when lcd_conn is specified

The newly introduced "lcd_conn" field for connected LCD panel type will
cause the original code to generate the warnings of incorrect lccr*.
This is unnecessary since well encoded LCD_* flags will not generate
incorrect combinition of lccr* bits. Skip the check if "lcd_conn" is
specified.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>