[ARM] 4434/1: PXA: remove PXA_IRQ_SKIP

1. PXA_IRQ_SKIP is defined to be 7 on PXA25x so that the first IRQ
   starts from zero. This makes IRQ numbering inconsistent between
   PXA25x and PXA27x. Remove this macro so that the same IRQ_XXXXX
   definition has the same value on both PXA25x and PXA27x.

2. make IRQ_SSP3..IRQ_PWRI2C valid only if PXA27x is defined, this
   avoids unintentional use of these macros on PXA25x

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