ARM: 7705/1: use optimized do_div only for EABI

In OABI configurations, some uses of the do_div function
cause gcc to run out of registers. To work around that,
we can force the use of the out-of-line version for
configurations that build a OABI kernel.

Without this patch, building netx_defconfig results in:

net/core/pktgen.c: In function 'pktgen_if_show':
net/core/pktgen.c:682:2775: error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'
net/core/pktgen.c:682:3153: error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'
net/core/pktgen.c:682:2775: error: 'asm' operand has impossible constraints
net/core/pktgen.c:682:3153: error: 'asm' operand has impossible constraints

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>