lmb: Avoid to add identical region in lmb_add_region_flags()

In case lmb_add_region_flags() is called with the same parameter than
an already existing lmb and this lmb is adjacent to its previous lmb with
different flag, this lmb is added again.

Instead breaking the loop, continue, at the next iteration, we are able
to detect that this region already exist.

Issue reproduced on STM32MP157-DK2 with SCMI DT, bdinfo command's output
shows:

Before this patch, the last LMB [0xde000000-0xdfffffff] is duplicated:
...
lmb_dump_all:nnn
 memory.cnt = 0x1 / max = 0x2
 memory[0]      [0xc0000000-0xdfffffff], 0x20000000 bytes flags: 0
 reserved.cnt = 0x6 / max = 0x10
 reserved[0]    [0x10000000-0x10045fff], 0x00046000 bytes flags: 4
 reserved[1]    [0x30000000-0x3003ffff], 0x00040000 bytes flags: 4
 reserved[2]    [0x38000000-0x3800ffff], 0x00010000 bytes flags: 4
 reserved[3]    [0xdaadf000-0xdfffffff], 0x05521000 bytes flags: 0
 reserved[4]    [0xde000000-0xdfffffff], 0x02000000 bytes flags: 4
 reserved[5]    [0xde000000-0xdfffffff], 0x02000000 bytes flags: 4
...

After this patch:
...
lmb_dump_all:
 memory.cnt = 0x1 / max = 0x2
 memory[0]      [0xc0000000-0xdfffffff], 0x20000000 bytes flags: 0
 reserved.cnt = 0x5 / max = 0x10
 reserved[0]    [0x10000000-0x10045fff], 0x00046000 bytes flags: 4
 reserved[1]    [0x30000000-0x3003ffff], 0x00040000 bytes flags: 4
 reserved[2]    [0x38000000-0x3800ffff], 0x00010000 bytes flags: 4
 reserved[3]    [0xdaadf000-0xdfffffff], 0x05521000 bytes flags: 0
 reserved[4]    [0xde000000-0xdfffffff], 0x02000000 bytes flags: 4
...

Fixes: 59c0ea5d ("lmb: Add support of flags for no-map properties")

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>