tune-cortexa32: Fix libgcc-initial build issue for cortex-a32

tune-cortexa32: Fix libgcc-initial build issue for cortex-a32

When we try to build images for machine which is tuned for
cortex-a32, then libgcc-initial recipe fails to build with
below error message.

-- snip --
configure:3529: aarch64-poky-linux-gcc  -mcpu=cortex-a32+crc -fstack-protector-strong  -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=.../tmp/work/aarch64-poky-linux/libgcc-initial/9.2.0-r0/recipe-sysroot -o conftest  -O2 -pipe -g -feliminate-unused-debug-types -fmacro-prefix-map=.../tmp/work/aarch64-poky-linux/libgcc-initial/9.2.0-r0=/usr/src/debug/libgcc-initial/9.2.0-r0                      -fdebug-prefix-map=.../tmp/work/aarch64-poky-linux/libgcc-initial/9.2.0-r0=/usr/src/debug/libgcc-initial/9.2.0-r0                      -fdebug-prefix-map=.../tmp/work/aarch64-poky-linux/libgcc-initial/9.2.0-r0/recipe-sysroot=                      -fdebug-prefix-map=.../tmp/work/aarch64-poky-linux/libgcc-initial/9.2.0-r0/recipe-sysroot-native=   -Wl,-O1 -Wl,--hash-style=gnu -Wl,--as-needed -fstack-protector-strong -Wl,-z,relro,-z,now conftest.c  >&5
aarch64-poky-linux-gcc: fatal error: unknown value 'cortex-a32+crc' for '-mcpu'
-- snip --

- Replacing TUNE_FEATURES from aarch64 to armv8a will solve the above
build issue.
- Changed BASE_LIB to 'lib', as cortex-a32 is a 32bit ARMv8a architecture.

The sample machine config file (qemuarma32.conf) used to reproduce
the error looks like:

-- snip --

require conf/machine/include/tune-cortexa32.inc
require conf/machine/include/qemu.inc

KERNEL_IMAGETYPE = "Image"

SERIAL_CONSOLES ?= "115200;ttyAMA0 115200;hvc0"

KMACHINE_qemuarma32 = "qemuarm64"
-- snip --

Signed-off-by: Jagadeesh Krishnanjanappa <workjagadeesh@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>