[ARM] 3192/1: Remove gpio_isr_line_clear() API from IXP4xx

Patch from Deepak Saxena

Other than interrupt masking purposes, this API is only used when
configuring interrupt lines and this patch moves that functionality
directly into the ixp4xx_set_irq_type() implementation as board level
PCI code should not need to worry about those details.

Signed-off-by: Deepak Saxena <dsaxena@plexity.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>