config: nxp: vf610: Remove CONFIG_SYS_MALLOC_F_LEN

config: nxp: vf610: Remove CONFIG_SYS_MALLOC_F_LEN

The commit c69103218ee4 ("i2c: mxc_i2c: add DM_FLAG_PRE_RELOC flag")
has enabled by default the i2c initialization in the pre-relocation
phase.
It turned out that vf610 based boards had too small SYS_MALLOC_F_LEN
pool size.

As a solution the explicit value of CONFIG_SYS_MALLOC_F_LEN for all
vf610 based boards has been removed from their configs.

Instead, the default value of 0x2000 is now used, which causes boards
to work correctly again. This approach has been tested on BK4 device.

Signed-off-by: Lukasz Majewski <lukma@denx.de>