arm: allwinner: Fix padconf for interrupts information

Add a eint_bank member to the allwinner_pins structure.
On Allwinner SoCs not all pins can do interrupt.
Older SoC (A10/A13 and A20) there is a maximum number of interrupts
set to 32 and all the configuration is done in the same registers.
While on "newer" SoCs (>=A31) interrupts registers are splitted per
pin bank (i.e. all interrupts available in bank B will be configured
with a sets of registers and the one in bank G in another set).
While here set the names to all interrupts function to
pX_eintY where X is the bank name and Y the interrupt number.

To whom ever in the future look at the H5 manual and notice that the bank F
have interrupts support : This isn't true, trust me.

MFC after: 1 month